In 2009, Marco Rubio was a plucky challenger for the open Senate seat in Florida, taking on incumbent Republican Gov. Charlie Crist. Though Rubio was trailing in the polls, one leading conservative activist thought he had real potential and vowed to help him.

"When Marco Rubio ran for the Senate in Florida, I think I was the first one to endorse him," said Phyllis Schlafly. "I made a trip down to Florida in 2009 just for the purpose of helping him."

But Schlafly, a legendary conservative activist, author and WND columnist, now says she is bitterly disappointed by Rubio's record.

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"Once he got elected, he betrayed us all," she told WND. "He said he was against amnesty and against the establishment. And once he got in, right away, he became an agent of the establishment. And now, of course, he's big for amnesty and letting all the illegal immigrants in. He betrayed us a number of times on that issue."

Schlafly said she was startled at the magnitude of Rubio's "betrayal" on amnesty.

"It was so public," she said.

"He's a lackey for the establishment now," she said. "There's no question they're picking up as Plan B – or maybe Plan C in this election cycle, or whatever we're on now – but he certainly is an establishment agent."

Watch the infamous video of Marco Rubio repeating himself over and over in the GOP debate in New Hampshire, Saturday, Feb. 6, 2016:

Rubio has been moving up in the polls since his third-place finish in the Iowa caucuses. But Rubio's record has drawn new attention since Sen. Rick Santorum, after dropping out of the presidential race and endorsing the Florida senator, found himself tongue tied when asked on MSNBC to name Rubio's greatest accomplishment.

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Rubio is best known for co-sponsoring the "Gang of 8" immigration amnesty bill, partnering with Sen. Chuck Schumer, D-N.Y., to allow a path to citizenship for illegal immigrants and dramatically increase legal immigration. Rubio was also identified by Sen. Robert Menendez, D-N.J., as the person designated to "neutralize" and "proselytize" conservative opposition.

Schlafly urged conservatives not to underestimate the importance of the immigration issue.

"Immigration right now is the biggest issue. All you need to do is look at Europe, and you can see that," she said. "But there are other issues like trade where Rubio has aligned with the establishment against the American worker."

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Watch Rubio clash with Sen. Rand Paul, R-K.Y., on immigration during the Jan. 28 GOP debate:

Though Rubio has been criticized for his poor attendance record in the Senate, he did manage to attend the session that granted President Obama powers to fast-track the Trans-Pacific Partnership as well as future trade agreements.

"Trade is a big issue," Schlafly argued. "The whole thing with how they are pushing these trade agreements and mass immigration is a cheat and a lie to the American people. And Rubio has joined the group that is pushing it."

Schlafly also criticized Rubio's foreign-policy credentials, as early in his term of office the freshman Florida senator enthusiastically backed President Obama’s campaign to remove the regime of Moammar Gadhafi in Libya.

Libya has since become a stronghold for ISIS.

"That didn't get us anywhere," said Schlafly.

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Schlafly, who has spoken highly of both Donald Trump and Sen. Ted Cruz, slammed "the establishment's" determination to select the Republican candidate.

"They're the people who have been picking losers all these years, and we want the grassroots to have a crack at it," she said.

She criticized Rubio as just the latest front man for the "kingmakers" she has denounced her entire career.

The narrative of Rubio as the "establishment choice" is also becoming part of the presidential campaign. Ted Cruz, campaigning in New Hampshire after his victory in Iowa, slyly has portrayed Rubio as the choice of the elites rather than the grassroots.

"I understand that in the media newsrooms and in the Washington establishment circles, Marco is the chosen one," he said.

He also joked, "In the media's telling, bronze is the new gold," referring to the widespread treatment of Rubio's third-place finish in the Iowa caucuses as a great success.

Schlafly urged conservatives not to take any chances with the election.

"Just look at what [Sen.] Jeff Sessions said – this is the last chance to save the America," she said. "Immigration is the issue."

She dismissed any hopes Rubio could redeem himself to conservatives.

"As soon as he got in there, he betrayed us all," she reiterated. "Don't make it look like I'm supporting him now."