Editor's note: This story has been updated throughout.

RINGSTED, Iowa — In the homestretch before the Iowa caucuses, Ted Cruz's presidential campaign appears to be refocusing some of its attention on a Republican opponent not named Donald Trump: U.S. Senate colleague Marco Rubio. 

On the airwaves and on the stump, Cruz and his allies are revisiting their criticism of the Florida senator after a month spent mostly expending its energy on Trump, the leader of the GOP pack here in most polls this month.

In recent days, Cruz's campaign and outside groups have released at least half a dozen ads aimed at undercutting Rubio's conservative credentials, mostly sharply over his involvement in immigration reform efforts in 2013. One of the spots says Rubio "betrayed" the trust of voters with his authorship of the so-called "Gang of Eight" bill. Another brands Rubio a "Republican Obama," citing his positions on immigration and taxes. And another commercial deploys U.S. Steve King of Iowa, an immigration hardliner supporting Cruz, to testify to how hard Cruz fought the Gang of Eight legislation.

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On the campaign trail, the Texas senator has upped his direct references to Rubio, naming him along with Trump while discussing, for example, candidates who he says did not respond forcefully enough to the U.S. Supreme Court's decision last year making gay marriage the law of the land. On Friday morning, Cruz voluntarily mentioned Rubio while warning Iowans about not getting "burned again" by two-faced politicians.

“Marco Rubio has gone on Univision and said in Spanish, ‘No, no, no, I wouldn’t rescind amnesty,'" Cruz said here in this northwestern Iowa city while pledging to repeal Obama's executive orders if elected president. 

Cruz's campaign insists the focus on Rubio is not a change in strategy, and by the end of Friday, it was pushing back on reports that it was growing worried about Rubio in Iowa. "The notion of the 'scramble' is ridiculous," a senior campaign official said, describing the torrent of ads as a congruent response to Rubio's charge at a debate Thursday that Cruz's campaign is "built on a lie." 

At the same time, campaign officials did not deny the target of their TV advertising in Iowa was shifting from Rubio to Trump, whom Cruz has said he is in an "absolute dead heat" with in the Hawkeye State. After the seventh Republican debate Thursday in Des Moines, Cruz campaign manager Jeff Roe told reporters he still views Iowa as "clearly" a two-man race between the Cruz and Trump, who did not attend the debate.

"We've been pointing out his record for all January, really," Roe said of Rubio. "We spent more emphasis on Trump for a while, more emphasis on him for a while. We have a clear contrast with both campaigns in different ways, and we're making sure that both campaigns and the voters have a chance to see the differences." 

On Friday in Fenton, Iowa, Cruz brushed aside a reporter's question about whether he sees Rubio as a new threat, saying he's focused on his own campaign.

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Rubio and his supporters, meanwhile, have been glad to tout attacks from pro-Cruz forces as a sign of the Floridian's gains in Iowa, where he has long registered in polls as a distant third behind Cruz and Trump. 

"I don't think there's any question Marco's on the rise," Rubio spokesman Alex Conant told reporters after the debate. "Every single campaign is attacking him, both in the debate and on TV."

In a statement Friday night, another Rubio spokesman, Joe Pounder, called one of the ads from pro-Cruz forces a "deliberate lie to deceive Iowa voters because he knows Marco is gaining momentum."

The Rubio bashing began before Cruz even took the microphone at his first event Friday in Iowa. Introducing Cruz in Ringsted, U.S. Rep. Louie Gohmert of Texas recalled how members like himself were disappointed to see Rubio author the Gang of Eight bill, which has become toxic to many Republican primary voters.

The immigration reform measure, which would have provided a path to citizenship for people in the country illegally, passed the Senate but failed in the House.

"We were really excited when a guy won the Senate race in Florida saying, 'I will stop any amnesty,'" Gohmert said, turning to King for validation. Instead of fulfilling the campaign promise, Gohmert added, Rubio "became the the face of amnesty bill. You have no idea how crushed we were."