Ted Cruz is mounting an aggressive effort to regain his Iowa lead, joining backers in an ad blitz against front-runner Donald Trump that casts him as an out-of-touch liberal, while Trump barnstorms the state to make final arguments before Monday’s caucuses.  

Cruz in recent weeks has seen his Iowa numbers dip following a surge that lasted from mid-November to early January. Trump has recaptured the lead in recent polls conducted by Fox News, Quinnipiac University and others.

But the race remains close, and the two candidates have turned up their attacks on each other.

The Cruz campaign just put out an ad, running statewide in Iowa, that plays old clips of Trump describing himself as “pro-choice” – and once again hammers Trump for his “New York values.” It then plays a recent campaign clip in which Trump jokingly said, “How stupid are the people of Iowa?”

Trump, meanwhile, called Cruz a “liar” who “looks like a jerk,” in an interview Tuesday.  

The attacks, by both candidates, started only in recent weeks, with Trump launching the first anti-Cruz ad, accusing him of supporting “amnesty” for illegal immigrants in the United States. The attacks and counter-attacks -- including those in debates and on the campaign trail -- have continued essentially nonstop with the Cruz camp piling on with more on Tuesday.

Another ad from a pro-Cruz super PAC argues Trump, if elected, would support taxpayer-funded, universal health insurance, based on a CBS interview last year in which Trump argued everybody in the country should have coverage.

“First there was HillaryCare, then there was ObamaCare. We can’t afford TrumpCare,” the narrator says in the 30-second spot, part of recently announced, $2.5 million ad buy from the super PAC Keep the Promise I.

The other ad this week by the group -- titled “Extreme” -- suggests Trump would support partial-birth abortion, apparently targeting the evangelicals and other conservatives for which Cruz and Trump are competing.

“Donald Trump is not a conservative because he’s extreme on abortion,” the narrator says at the start of the ad, which ends with a clip of Trump saying in 1999 he is “pro-choice in every respect.”

Trump now says he’s pro-life.

How well the attacks resonate will not be clear until caucus night.

Some political analysts suggest the head-on battle will hurt both Cruz and Trump, which might allow a more “establishment” candidate like Florida Sen. Marco Rubio, Ohio Gov. John Kasich, or New Jersey Gov. Chris Christie to climb.

“There is a decent chance, given their personalities, that they will make each other maximally unattractive and go down in each other’s death embrace,” New York Times columnist David Brooks wrote Tuesday.

Meanwhile, Trump, a master at free TV advertising, is continuing his attacks on Cruz on political shows and on the campaign trail.

Trump called Cruz a “liar” in an MSNBC interview Tuesday. “Nobody likes him,” Trump said.

And Trump continues to question whether Cruz, an American citizen born in Canada, is eligible to run.

“He hit me, I hit him,” Trump said Saturday at a rally in Pella, Iowa. “He has legitimate problems. No one knows if he can run for president. Constitutional lawyers [are] saying he can't. I know he was born on Canadian soil. He's already had two lawsuits filed.”