Right now, Marco Rubio's odds of winning the Republican nomination look very good. But a huge reason he looks so strong is that so far no one has tested his biggest weakness. On the crucial issue of immigration that has already upended the contest via the surge of support for Donald Trump, Rubio is on the wrong side of the party's rank-and-file voters and in lockstep with the elements of the establishment they most mistrust. His record on the issue isn't just wrong from a Tea Party point of view, it's downright weaselly — arriving on the political stage as a champion of their cause only to draft a bipartisan bill betraying them on a huge issue.
Much of the current bullishness on Rubio reflects a media community that's been primed to believe in the power of Marco by the fact that he is transparently the candidate Democratic Party professionals most fear. Under the circumstances, the GOP donor class's initial coordination around Bush always looked like a bit of a blunder, so the idea of a rapid shift toward Rubio among Republican economic elites seems like a very plausible scenario.
But Democratic Party operatives, Republican economic elites, and Marco Rubio (throw in most political reporters, too) all have something in common that puts them at odds with rank-and-file Republicans — they think granting legal status, work permits, and a path to citizenship to millions of Latin American immigrants who have been living and working in the United States illegally for years is savvy politics, sound economics, and good ethics.
Rubio has evaded the immigration issue
In an excellent June National Review article, Jim Geraghty ran through Rubio's serious problems on immigration — running in 2010 as an amnesty opponent, co-authoring the 2013 bipartisan Senate immigration bill, then swiftly abandoning the bill and disavowing the entire approach, but doing so on procedural rather than substantive grounds.
Yet one surprising aspect of Geraghty's story hasn't held up well. Geraghty predicted that during debates "every one of [Rubio's rivals] will surely remind GOP primary voters of Rubio’s role in creating and supporting the 'Gang of Eight' comprehensive immigration-reform bill" and that "it’s inconceivable that Rubio’s foes won’t hit him on this issue early and often."
That certainly seems like what you would say if you wanted to beat Rubio. But so far none of the other candidates are doing it. Mark Krikorian, the executive director of the conservative Center for Immigration Reform, called Rubio's brief remarks on immigration in the third debate "either clueless or lying … a useful caution for those excited by his genuine rhetorical gifts." But nobody on stage called him on it.
That's because after the exit of Scott Walker from the race, the Republican primary has bifurcated. Rubio and Jeb Bush are in a dogfight for the loyalty of the establishment donor class, while everyone outside that circle is fighting to either tear down the establishment (Trump, Cruz) or bang their way into the favored circle (Christie, Kasich) or else is just on a random self-promotional trip. Bush isn't hitting Rubio on immigration because they don't really disagree, and Bush isn't smart enough or talented enough to come up with an argument. And the outsiders aren't hitting Rubio because he hasn't become sufficiently prominent to work as an establishment foil.
The chickens will (probably) come home to roost
One reason Rubio has looked so good thus far, in other words, is that his biggest and most obvious weakness hasn't been on the table. That's a lucky break, but it's hard to see how it will last.
If by the next debate Rubio has succeeded in clearly displacing Jeb Bush as the establishment favorite, then the incentives for Cruz and Trump (or even Christie or Fiorina) to start lighting into Rubio on immigration get a lot bigger. But as Cruz himself outlined to Shane Goldmacher, his current plan is to focus on consolidating the vote that he is currently splitting with Trump and Ben Carson and only later turn on whomever the strongest establishment-friendly candidate will be.
"Three months ago," Cruz said, "every observer would have assumed that Jeb Bush would run away with being the moderate establishment candidate. At this point, I have no idea who the moderate establishment candidate will be."
Only when it becomes clear that Rubio is the guy will Cruz start unleashing the obvious lines of criticism. Facing that argument isn't necessarily an insurmountable problem for Rubio, but it does seem like a serious one. For all the entertainment value of this year's Republican infighting, the GOP is quite broadly unified on a policy level in favor of big regressive tax cuts and large-scale rollback of the Obama regulatory agenda. Immigration is the exception. A large minority of Republican members of Congress — including Marco Rubio — agree with Barack Obama and Hillary Clinton about the desirability of legal status and a path to citizenship. A majority of GOP elected officials and the vast majority of rank-and-file Republicans do not.
At a moment when many conservative activists feel they have been betrayed by party leaders, the mere fact that GOP elites like Rubio does nothing to assuage concerns about his stance on immigration. On the contrary, wariness of Rubio as soft on immigration and wariness of the establishment as eager to sell out the base form a powerful mutually reinforcing counter-Rubio narrative. It hasn't hurt him thus far because it simply hasn't been tried. But it's nearly inconceivable that Rubio can keep coasting much longer without facing his core vulnerability.