On talk radio, on the campaign trail and on televisions in states like Iowa, Mr. Rubio is suddenly facing a torrent of criticism from within his own party unlike anything he has faced so far in the presidential race…

People who saw Mr. Rubio speak near Des Moines the other day found their windshields plastered with black-and-white fliers that mocked him as “Chuck Schumer’s amnesty pitchman.” If Mr. Rubio is elected president, warned the fliers, which were noticed by a freelance journalist, he would support liberal immigration policies and “impose them by force on Americans.”

Mr. Rubio’s struggle to mollify Republicans who believe he betrayed conservative principles for political convenience – two years of outreach, apology and labored professions of a lesson learned – has never had higher stakes. Right now he is trying to break out beyond the third- or fourth-place spot he holds in many polls by peeling away support from conservative favorites like Mr. Cruz and Ben Carson.

His recent attacks on Mr. Cruz are backfiring as some influential conservatives are now rallying to Mr. Cruz’s side and denouncing Mr. Rubio.

But in his first venture into presidential politics, as a policy aide on George W. Bush’s 2000 presidential campaign, Mr. Cruz, of Texas, advocated a far more equivocal answer to the question of what to do with those in the country illegally…

“America is stronger with the many immigrants who come here to make a new life and participate in the American dream,” Mr. Cruz wrote in capital letters about legal immigrants at the document’s outset…

Mr. Cruz urged Mr. Bush, again in capital letters, to state his opposition to illegal immigration and to urge enforcement of border restrictions.

“But, at the same time,” he added in the next sentence, “we need to remember that many of those coming here are coming to feed their families, to have a chance at a better life.”…

“One of the reasons I was so eager to help Bush is the way he has described himself, as a compassionate conservative,” Mr. Cruz told a Princeton alumni publication in 2000, not long after writing the memo. “That’s how I have always conceived of my own political views.”

“Rubio’s offense is his best defense there, no question,” said Curt Anderson, an unaligned GOP operative who had guided Bobby Jindal’s campaign. “They clearly did their homework, and they were ready for it. I think it was well played.”…

In battling over the particulars of immigration, Rubio isn’t likely to score any points — but that’s not his objective. “I don’t think it means anything for Rubio, but it could mean something for Cruz in that he’s handled it poorly,” Anderson said. “I think the only way to go at Cruz is to go at his genuineness or lack thereof, and the fact that everything is contrived. In that sense, I think it’s smart.”

According to sources close to the campaign, the unifying thread of Rubio’s case against Cruz won’t be immigration or national security or any single policy issue. It’ll be his perceived tendency to say different things to different audiences and an attempt to convince voters that the candidate purporting to be a straight-talking anti-establishment outsider is anything but that…

Now, the Rubio game plan is not to let up. Pounder and his team believe they have ample material to fill in a composite sketch of Cruz as a political opportunist: his praise for Edward Snowden, opposition to the NSA’s former metadata surveillance program and his closed-door comments criticizing Trump even as he continues to show remarkable deference to him in public.

I can understand why Rubio is eager to undermine Cruz on this issue, but because of his record he is the least credible critic of Cruz’s slipperiness. Rubio has tried to have it both ways on immigration for the last three years, which is why so many conservatives distrust him, and his main argument against Cruz is that Cruz is just like him. That’s also not very smart if the goal is to reassure conservatives that Rubio can be trusted, since the attacks on Cruz are a reminder that Rubio was a big supporter of the Gang of Eight bill that Cruz actually opposed. The attacks also remind conservatives why they dislike that bill so much, which makes Rubio’s vulnerability on this issue that much worse. Even if Rubio proves that Cruz is slippery and can’t be relied on to oppose immigration “reform,” all that he does is convince Cruz’s restrictionist and enforcement-first voters to rally behind Trump. They don’t convince any of them that they should support Rubio. There is no scenario in which hitting Cruz on immigration benefits Rubio, and by continuing the argument Rubio is likely alienating more conservative supporters that he needs than he is gaining.

Facebook, Microsoft, and Silicon Valley back Marco Rubio. Mark Zuckerberg is a social-justice CEO who panders to Hispanics with his pro-amnesty, anti-deportation advocacy; Facebook is an H-1B-visa-dependent company working hard to obliterate hurdles to hiring an unlimited stream of cheap foreign tech workers. It’s no coincidence that Facebook’s lobbying outfit, FWD.us, was waging war on Senator Cruz online this week in parallel with Senator Rubio’s disingenuous onstage attack…

Paul Singer backs Marco Rubio. The hedge-fund billionaire announced his support for Rubio in October. Amnesty is and always has been a top agenda item for Singer, who, along with fellow hedge-fund billionaire George Soros, helped fund the National Immigration Forum. NIF propped up a faux-grassroots initiative of religious conservatives, dubbed the Evangelical Immigration Table, to lobby for the Gang of Eight…

Rove/Bush-tied front groups back Marco Rubio. The American Action Network is a Big Business GOP lobbying organization led by former senator Norm Coleman (R., Minn.), and co-founded with John McCain adviser/fundraiser Fred Malek. AAN shared its offices with amnesty peddler Karl Rove’s American Crossroads in D.C. AAN’s “action arm,” the American Action Forum, was founded in February 2010, and Jeb Bush sat on the AAF board. AAN proceeded to spend a whopping $25 million to attack conservatives who opposed amnesty…

When you need the truth about which Beltway crapweasels are selling out America, always follow the money.

The truth is somewhere in the middle. Cruz always opposed Rubio’s bill as written and played an important role in its defeat. He clearly understood the importance of the path to citizenship to its Democratic supporters and knew they would never accept his compromise offer of green cards with no right to naturalization. He hoped to expose supporters’ commitment to citizenship. But his contemporaneous statements make plain that this middle ground was his actual substantive policy preference and not solely a ploy to sink the Gang of Eight…

As my colleague David Drucker has noted, while Cruz fights fierce battles with the left he prefers to carefully navigate issues that divide conservatives. Immigration is one such issue. Just as Cruz once favored increasing legal immigration levels and now would freeze current levels in place until the U.S. labor market tightens, he remains anti-amnesty but now adheres to a stricter definition of the term.

In other words, as the conservative mood on immigration has hardened so has Cruz’s position. He should just acknowledge his evolution…

Rubio’s immigration dilemma is similar to Mitt Romney’s on RomneyCare in 2012 — he can’t celebrate his biggest legislative initiative. Cruz should avoid a Mitt Romney dilemma of his own. Conservatives were never unhappy that Romney moved in their direction on issues. They simply did not want him to insult their intelligence by pretending his past positions never existed.

Ted Cruz, take note.

It is a habit with Rubio, a candidate aiming at moderate and conservative voters who often seems to advocate two positions at once. He tells voters he has a personal view on the subject — which might be abortion, immigration, Syrian refugees and gay marriage. But he also has a view of what is politically possible. Which, usually, is not what he personally wants.

That tactic allows Rubio to offer two right answers to the same question, and let him carve out wiggle room on topics where none seemed possible…

“I am personally open — after all that has happened and after 10 years in that probationary status where all they have is a permit — I personally am open to allowing people to apply for a green card,” Rubio said, talking about his views on whether and how to offer legal status to immigrants who entered the country illegally. Then the caveat: He is also open to not following his own personal views. If that’s what people want.

“That may not be a majority position in my party, but that’s down the road,” Rubio said. “You can’t even begin that process until you prove to people” that border security is working, he said…

“I don’t know exactly where he stands on that,” said undecided Republican voter Stephanie Hooton of Derry, N.H., before the barn event, a “No-B.S.” barbecue hosted by Scott Brown, the former U.S. senator from Massachusetts. Hooton added: “Some sort of amnesty, I think, is part of his plan.”

At the debate, Rubio alleged that Cruz was to his left on immigration because Cruz supported “legalization.” Cruz claimed he never supported such a thing. In the aftermath, he has taken the time-honored political path we call “clarification.’ While he is in no way being dishonest, he is definitely lawyering…

Imagine how this would have gone if [Donald Trump] had been in that exact situation. What would he have done?…

He would have shrugged it off. He would have made a face and said “come on Bret. Look it’s very simple. I was trying to get what I wanted from a negotiation. I wanted to stop what they were doing and I got news for you, I did it.” And if Bret pressed him again, he would have waved his hands and said “I make deals. OK? That’s what I do. I know deals. And I worked this deal, and I won this deal, and that’s what Americans care about.”

And people would have loved him for it. He wouldn’t be on defense right now. You can learn from anyone, including Donald Trump. This is worth learning.