Three Republican presidential candidates —  Sens. Ted Cruz and Rand Paul and former HP CEO Carly Fiorina — all took aim at rival Marco Rubio on Thursday, suggesting the Florida senator’s rhetorical conversion on immigration is not credible.

The broadsides, made by each during separate appearance on “The Laura Ingraham Show,” are further indication that the candidates believe the ascendent Rubio has supplanted former Jeb Bush as the establishment Republican favorite in the 2016 presidential race. After helping craft the “Gang of Eight” amnesty bill, Rubio has in recent days been suggesting he takes a tougher line on the issue.

Paul predicted that Rubio’s $1 trillion child tax credit plan would funnel untold millions of dollars to illegal aliens. He pointed to a recent inspector general’s report estimating that the fraud rate of existing tax credits is about 25 percent. Some $4 billion has gone to illegal immigrants, Paul said.

“Rubio’s tax plan would explode payments to illegal aliens,” he said. “And this is a real problem. Until we fix the current tax credits, do we really want to double and triple the amount of tax credits we’re giving?”

Paul and Cruz both noted that Rubio voted in lock-step with Democrats on the Senate Judiciary Committee in 2013 to block their efforts to amend the Gang of Eight bill.

Paul’s offering would have forced Congress to vote every year to certify that the U.S.-Mexico border is secure before other provisions in the bill could go forward.

“There was a secret deal made between Rubio and (New York Democratic Sen. Chuck) Schumer to block all the conservative amendments,” he said.

Rubio, Paul added “will be the establishment candidate. He will not fight the status quo.”

Rubio, Paul added “will be the establishment candidate. He will not fight the status quo.”

That immigration bill, which would have provided a path to citizenship for illegal immigrants, passed the Senate but died in the House.

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Fiorina, meanwhile, said she does not buy Rubio’s recent conservative rhetoric on immigration and trade.

“This is what politicians do, Laura, they talk,” she said. “And specifically, they say what they think they need to say to get elected. Honestly, we shouldn’t be surprised. Marco Rubio wouldn’t be the only politician to change his mind on something. And yes, you’re quite right, he’s changed his mind about a lot of things.”

Cruz in 2013 proposed doubling immigration from 675,000 to 1.3 million and increasing the cap on H-1B visas for high-tech workers from 65,000 to 325,000. He told Ingraham that he made the proposals, in part, to “demonstrate the hypocrisy of the Democrats” during the debate over comprehensive immigration reform.

His current view on legal immigration increases?

“I don’t believe that’s a good idea,” he said.

Cruz said he soured on the value of the H-1B visa after reports of misuse by U.S. corporations. Designed to give companies flexibility to bring in foreign workers with specialized skills, he said, the program instead has been used by companies to replace American employees with workers who do not have unique skills.

“We have seen serious abuses,” he said, adding that he is working with Sen. Jeff Sessions, R-Ala., on legislation to crack down on the practice.

He called the practice “another manifestation of the lawlessness of the Obama administration,” which has failed to enforce the rules of the visa.