LAWTON, Okla. — For weeks, Ted Cruz supporters have distressingly referred to it using different terms: the Trump train; the Trump steamroller — some unprintable phrases as well. 

Whatever they call it, the U.S. senator from Texas is throwing himself in front of it with full force as he nears Super Tuesday, which he has branded "the most important day in this entire presidential election." As he crisscrosses the South, Cruz is making his most explicit and comprehensive case against Trump, looking to blunt what some Republicans see as the billionaire's unstoppable momentum

"If you nominate a candidate who has agreed with Hillary Clinton on issue after issue after issue, if you nominate a candidate who's afraid to hand over his tax returns, if you nominate a candidate who's described Hillary Clinton as one of the greatest secretaries of state in history, if you nominate a candidate who's given $100,000 to the Clinton Foundation — that is a recipe for losing and electing Hillary Clinton as president," Cruz told supporters here at the county fairgrounds Sunday night.

As he campaigned across the Sooner State on Sunday, Cruz sought to project strength, arguing that he is "running neck and neck with Donald Trump in states all across Super Tuesday" — a claim largely refuted by public polling. He went even further in Lawton, saying he is "effectively tied" with Trump in Oklahoma — a state he described as a "battleground" on Tuesday.

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Before a rally Sunday afternoon in Oklahoma City, Cruz said he was feeling particularly good about the Sooner State because it has a closed primary system. "That means it's actually Republicans who are voting in the primary," said Cruz, who has suggested Trump benefited from Democratic support in the Palmetto State, which allows voters from either party to participate in its GOP nominating contest.

In any case, it is Trump who has the wind in his sails as he barrels toward Tuesday, when 11 mostly southern states are set to vote in what is being called the "SEC primary." The billionaire delivered a blow to Cruz on Sunday afternoon, when he unveiled the endorsement of U.S. Sen. Jeff Sessions of Alabama, an immigration hardliner whom Cruz has described as a close ally. 

As word got out that Sessions was set to back Trump, Cruz declined to weigh in on the news, telling reporters in Oklahoma City that he willl "wait to comment on endorsements until they happen." Minutes later, it happened — specifically on stage before an estimated 32,000 people in Madison, Alabama. 

While Sessions' endorsement of Trump was not stunningSessions appeared onstage with Trump at a rally last year in Alabama — it packed a sting for Cruz, who frequently touts how he stood "shoulder to shoulder" with Sessions to defeat immigration reform efforts in 2013. Sessions offered an extended defense of Cruz when the candidate stumped two months ago in Daphne, Alabama — at the height of his battle with Rubio over his immigration record. 

Cruz set aside his regular sparring with Rubio and overwhelmingly focused Sunday on Trump, most sharply criticizing his use of foreign labor to build some of his properties. Acknowledging Trump's penchant for putting his name on buildings, Cruz on Saturday night suggested an addendum to the Trump Tower sign: "Built by illegal immigrants."

"You don't get to abuse the immigration laws and pretend to be a champion of working men and women," Cruz said at a rally Sunday morning in Tulsa, echoing an argument that Rubio has been making since the 10th GOP debate Thursday in Houston. 

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Cruz was already going after Trump before his first event Sunday in Oklahoma. In a series of national TV interviews that aired as Cruz was going to church in Arkansas, the Texas senator raised the possibility that Trump is refusing to release his tax returns because they he has connections to organized crime. 

Cruz's efforts to stunt the billionaire's momentum got a boost Sunday from conservative media personality Glenn Beck, perhaps Cruz's most vocal Trump critic. Introducing Cruz at the rally in Oklahoma City, Beck deemed Trump the "most dangerous man to ever be seriously considered for president of the United States."

Cruz is asking voters to anoint him the chief alternative to Trump in the Super Tuesday states, where expectations are high for the Texas senator given how much time and money Cruz has invested in them — and how openly he has talked about the SEC primary as the day when fortune will turn in his favor. On Sunday, Cruz was again predicting his campaign would have a "very, very good Super Tuesday." 

"He's the only one who's been to Oklahoma this many times," U.S. Rep. Jim Bridenstine said at the rally in Tulsa. "He came to my 40th birthday party in June!" 

Yet what Cruz faces in the Super Tuesday states is not unlike what he has encountered elsewhere: Even the best-laid plans can be blown up by Trump's rollicking candidacy. In a sign of how much things have shifted for Cruz, some of his supporters are now just hoping he can notch a resounding win Tuesday in his home state, which he is set to tour Monday with Gov. Greg Abbott and former Gov. Rick Perry.

"If he can defend his home turf, I think that shows that he's got some legs to the campaign," Cruz backer Rick Carpenter said as the senator's Tulsa rally let out, stopping short of predicting a Cruz victory elsewhere Tuesday. "A state like Oklahoma would certainly be a boost."