In 2013, freshman U.S. Sen. Ted Cruz of Texas said he had a plan to do something that seemed impossible. He could force President Obama to strip the funding from the landmark health care law that had come to bear his name — Obamacare — by threatening to shut down the government.

To some other conservatives, there was a problem with Cruz’s plan.

It still seemed impossible.

To succeed, Cruz needed a novel way to outmaneuver the Democrat-led Senate and then pressure Obama to undercut his signature domestic policy achievement.

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But Cruz didn’t have one. Instead, his critics said, he offered only a fanciful theory that if the GOP flirted hard enough with a shutdown, Democratic lawmakers and the White House might lose heart and surrender.

Grover Norquist, the influential anti-tax activist, likened Cruz’s strategy to a plotline in the satirical animated show “South Park,” in which a group of gnomes comes up with a brilliant plan to become rich. "Step 1 is: Steal all the underwear in South Park. Step 2 is: Mumumumbumbumbum,” Nor­quist said, making a nonsense sound. “And Step 3 is: Make a million dollars. And this [plan] reminded me of that episode.”

Josh Holmes, a former aide to Senate Majority Leader Mitch McConnell, R-Ky., said it was “like a toddler’s version of legislating.”

Cruz’s gambit didn’t work. Neither Senate Democrats nor Obama gave an inch on their cherished law. Instead, the government shut down for 16 days, and Republicans in Congress were blamed for it — including by other Republicans, who said they had distracted attention from the disastrous rollout of the HealthCare.gov website.

Today, the drama that surrounded the shutdown — including Cruz’s 21-hour Senate speech, in which he read “Green Eggs and Ham” to his daughters via the C-SPAN feed — is the defining moment of a Senate tenure that has helped make Cruz the favorite Republican presidential candidate for many conservatives.

To those supporters, the shutdown signaled the depth of Cruz’s commitment to rein in government.

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But for many Republicans in Congress, this was the episode that soured them on Cruz. Many suspect that he always knew his plan would fail but went ahead with it anyway — expecting that he would personally benefit from the exposure, even if his party lost a damaging fight.

“He knew that. He knew it. He knew it,” former senator Tom Coburn, R-Okla., said. “It wasn’t about the shutdown. It wasn’t about the Affordable Care Act. It was about launching Ted Cruz.”

On the campaign trail this year, none of Cruz’s fellow senators have endorsed him for president. And some GOP rivals have used the shutdown to criticize him.

Republican presidential candidate Marco Rubio, a senator from Florida who was a vocal supporter of Cruz during the shutdown, now uses it to call Cruz ineffective: “I’m the only one running that’s actually ever scored a victory against Obamacare,” Rubio says. He is referring to a bill that undercut a government program to bail out failing insurers. Rubio didn’t actually play a very substantial role in its passage. But it passed.

Sen. Lindsey Graham, R-S.C., a former presidential candidate and a longtime Cruz nemesis who is now backing former Florida Gov. Jeb Bush, cites the shutdown saga as proof that Cruz is shameless.

“What he did was stood up for Ted and threw the Republican Party under the bus,” Graham has said.

On the campaign trail, Cruz often talks about Obamacare, telling audiences that he will “repeal every word” of the health care law if he is elected president. But he refers to the 2013 battle infrequently. And he rarely utters the word “shutdown.”

Rick Tyler, a spokesman for Cruz’s campaign, said the senator doesn’t often say the word because shutting down the government was never his goal.

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“He didn’t pursue a government shutdown strategy. That’s not even sane,” Tyler said. “That would be a good thing to go out and campaign on? That wasn’t what he did. He led the fight to defund Obamacare.”

But even in Cruz’s telling of the story, his plan to defund Obamacare was based on a misreading of how other key players would react when he threatened a shutdown.

He says he thought Obama and top Democrats would be cowed. He says he thought Senate Republican leaders would be willing — at least in public — to take the risk.

In both cases, he was wrong.

“The reason it didn’t work is because Ted Cruz was the only candidate, the only senator, who campaigned on defunding Obamacare and followed through on his campaign promise. Nobody else did,” Tyler said, arguing that others said: "'Oh, we don’t have the votes. We’ll just give up.' That’s not leadership; that’s capitulation and appeasement and surrender."

If there was a blunder in Cruz’s plans, Tyler said, “the miscalculation was that when his colleagues campaigned on defeating Obamacare, he thought they meant it.”

The fullest explanation of that time, written from Cruz’s perspective, came in his 2015 book, “A Time for Truth.”

In it, Cruz begins the chapter about his own fight with a story from 160 years ago. Just before the Civil War, he writes, a Wisconsin abolitionist was punished for breaking the law to help a former slave escape to Canada. But later, Cruz says, the man was pardoned and vindicated.

“He was an American hero,” Cruz writes.

In the next paragraph, Cruz jumps from slavery to Obamacare, and from that American hero to himself.

“In Washington, pundits repeatedly intone that we had no plan, no strategy, and no hope of success,” Cruz writes. “I’ve got many personal faults, but, as a former Supreme Court litigator, failing to plan is not one of them.”

"It was the last gasp to stop it"

It was not Cruz’s idea, originally.

In 2013, conservative activists were looking for a new tactic to defeat the health care law, which had survived a Supreme Court challenge, before its first insurance exchanges opened Oct. 1. Republicans had tried passing standalone bills to repeal it, but the Senate killed them. The new plan was to use a bill that the Senate was obligated to pass — a spending bill to keep the government funded. They would pass a bill that paid for everything, except Obamacare.

“It was the last chance. It was the last gasp to stop it,” said Brent Bozell, chairman of the conservative group ForAmerica. “Did I think it was going to work? We knew it was going to be tough. Anything is possible. But we knew it was going to be tough.”

Cruz joined the “defund” effort early on and became its leading spokesman and an important legislative leader.

“The president is never going to sign a bill that defunds Obamacare,” CNN’s Candy Crowley told him on Aug. 25, 2013, with a shutdown a little more than a month away.

“You know, you may be convinced to that,” Cruz replied.

“You’re not convinced to that?” Crowley asked.

“I am not at all,” Cruz said.

In theory, his plan worked like this:

First, the House would pass a bill to defund the health care law.

Then came the Senate. Republicans had 46 seats there — not enough to pass a bill but enough to block one. So they’d block a vote on any Democratic version of the spending bill. In the meantime, Cruz would use lobbying and public pressure to swing wobbly Democrats over to his side.

Eventually, Obamacare opponents would have the 60 Senate votes they needed to pass Cruz’s bill and send it to the president.

At that point, according to Cruz’s plan, Obama might start to respond as he did during the debt-ceiling showdown two years earlier. In those negotiations, the threat of a government default was so scary that the White House and legislative leaders agreed to a series of drastic cuts known as the sequester.

Chip Roy, Cruz’s chief of staff at the time, described the debt talks as a “model” for Cruz’s strategy.

“We could get some pound of flesh out of the president and [then-Senate Majority Leader] Harry Reid,” Roy said. “That was always the endgame.”

But other Republicans believed that Cruz’s plan was too farfetched to work.

For one thing, Cruz would need to flip more than a dozen Democratic votes to get his idea passed by the Senate. And he’d need seven more Democrats to override a presidential veto. If Cruz couldn’t get them, ever, then Republican leaders were reluctant to gridlock the Senate and wait for the impossible to happen.

“Virtually everybody understood the absurdity of the tactic,” said Holmes, the former McConnell aide. “Look, we all support the idea of defunding Obamacare. But saying we were going to defund Obamacare” with 46 votes “in the Senate or shut the government down is absurd.”

But in the summer and fall of 2013, Cruz and conservative activist groups pressed on, pressuring other Republicans to go along with the plan. They tended to reduce the complex calculations of the fight — 60-vote thresholds, worries about presidential vetoes — into a test of Republican fortitude.

“How do we win the fight to defund Obamacare?” Cruz shouted at a rally in Dallas in the summer of 2013, part of a 10-city tour. “Don’t blink.”

Where the plan "went awry"

Step 1 worked, as Cruz wanted. The GOP-led House — pushed by conservatives who were coordinating with Cruz — passed a bill to cut off the health-care law’s money.

Now it was time for the Senate.

“Kind of like Evel Knievel crossing the Grand Canyon,” said former congressman Steve Southerland II, R-Fla., who voted for Cruz’s plan in the House. That was a joke: Knievel, the 1970s motorcycle daredevil, always boasted that he could jump the Grand Canyon. But he never actually did.

Indeed, here is “where the plan went awry,” Cruz says in his book.

“What we did not anticipate was that ... the GOP leadership team would decide to publicly, directly and aggressively lead the fight against the House Republicans and in favor of Obamacare,” he writes.

Senate Republicans did not gridlock their chamber, and several criticized Cruz for making them the villains.

The Democrats who ran the Senate were able to reject the House bill easily. Cruz never seems to have made a concerted effort to lobby red-state Senate Democrats, whom he described as the last key element of his plan to win over the Senate.

“I don’t ever remember hearing from Senator Cruz or his people,” said former senator Mark Pryor of Arkansas, who was perhaps the Senate’s most vulnerable Democrat at the time. He would lose his re-election bid to a Republican by 17 points. But he says he never felt pressure. “There was zero temptation for Democrats to shut down the government or defund Obamacare. No one on the Democratic side was interested in that at all.”

As the days ticked down to the shutdown, Cruz was criticized even by House conservatives, who thought he needed to do more to make his plan work. He gathered with top aides in a small office near the Capitol dome. He read to them from Psalm 40, recalled Roy, his former chief of staff.

The reading is a plea for deliverance from someone overcome by problems: “For troubles without number surround me. My sins have overtaken me, and I cannot see.”

Cruz then went to the Senate floor.

“I intend to speak in support of defunding Obamacare until I am no longer able to stand,” he said.

Cruz’s speech was, at its heart, a meditation on impossibility. He cited cases in which things that seemed impossible — the Continental Army’s fight against the British, the British fight against the Nazis, the mountain climbed by the Little Engine That Could — were difficult but possible.

His battle, Cruz said, was similar. “I think I can. I think I can. No, you can’t. No, you can’t. We can’t win,” he said. “You can’t stop Obamacare. It cannot be done. It is impossible.”

But, it turned out, he couldn’t.

In his book, he blamed Obama’s refusal to compromise on the president’s confidence in how the friendly media would tell the story.

“He knew his media lap dogs would report that it was Republicans who were refusing to compromise,” Cruz wrote.

Finally, on the 16th day of the shutdown, the Senate and the House voted to fund the health care law, ending the standoff without any of the victories Cruz wanted. Cruz and his allies blamed Senate Republicans, saying they had splintered without ever testing Obama’s resolve.

"With respect to Obama, it’s the road not taken. We don’t know. I can’t accept the premise that we miscalculated on Obama in the slightest," Roy said. "The Republican leadership literally cowered in the corner, afraid of the word 'shutdown.'"

Today, the sting from the standoff lingers among Cruz’s congressional colleagues.

"How can I say this nicely? He was still critical of those of us who pointed out the obvious shortcomings of his tactic, and he called us capitulators," Rep. Charlie Dent, R-Pa., said. "That’s not real leadership. That’s lemming leadership. It’s lemming leadership, is what it is."

Even so, while the shutdown earned Cruz enemies in Washington, his success thus far in the presidential race shows that it gave him credibility with the conservative base. When he was campaigning in Des Moines in the closing days before his victory in the Iowa caucuses this month, one of the men who introduced him uttered the S-word that Cruz avoids.

“When Ted Cruz shut down the government,” said Michael Berry, a conservative talk-radio host and Cruz ally.

The crowd roared.

Sean Sullivan of The Washington Post contributed to this report.