If a new CNN poll is correct, a majority of Republican voters are significantly to the right of pretty much every Republican elected official and every single Republican presidential candidate — including Donald Trump — on immigration.

The poll of 1,017 Americans, conducted July 22 through 25, shows that nearly two-thirds of Republicans believe the United States' priority in immigration policy should be "developing a plan to stop the flow of illegal immigrants into the US, and deporting those already here."

Mass deportation of unauthorized immigrants currently in the US has traditionally been a minority position even among Republicans and conservatives. As recently as 2013, when the Senate was considering a comprehensive immigration reform bill — which passed the Senate but never made it to the president's desk largely due to Republican opposition — only about a third of Republicans said that unauthorized immigrants "should not be allowed to stay" in the US.

It's typical for Americans to say that securing the border should be a priority. And because — as Greg Sargent points out in the Washington Post — the CNN poll asked the question in a somewhat unusual way by lumping border security in with deportation of current unauthorized residents, it's hard to say for sure that the poll reflects current Republican opinion. But there's some evidence that Republicans and conservatives have been trending in this direction for a while. And that should be extremely worrisome for Republican elected officials.

As immigration has become associated with Obama, opinion on mass deportation has polarized

Other recent polls haven't found quite as many Republicans willing to endorse mass deportation — but they've still found more of them than in the past. A Quinnipiac University poll showed 46 percent of likely GOP Iowa caucus-goers agreed that unauthorized immigrants should be required to leave the US (though majorities of white evangelicals, "very conservative" voters, and self-identified Tea Party supporters agreed). And in a Pew Research Center poll from June, 43 percent of Republicans and 45 percent of conservatives said that unauthorized immigrants should "not be allowed to stay." Compare that with 2013, when polls like Pew's were standard — and even a Fox News poll found only 22 percent of Republicans and conservatives endorsing "send all illegal immigrants back to their home country."

Maybe the spike in support for mass deportation in the CNN poll is, in part, a result of the Donald Trump Effect. Trump's surprisingly insurgent candidacy hasn't single-handedly put immigration back in the national conversation, despite what the candidate himself might claim, but it's definitely mobilized some deeply held feelings among the Republican base. (It's important to note, however, that Trump himself is open to a path to legal status for at least some unauthorized immigrants: "If someone's been outstanding," he told MSNBC on Friday, "we [would] try and work something out.")

But the trend appears to go back farther than that. From February 2014 to December 2014, according to Pew, support for legal status for unauthorized immigrants (as opposed to making them leave) dropped 11 percentage points among Republican voters, and 14 percentage points among self-described Tea Partiers. And in fall 2014, right after President Obama announced executive actions protecting millions of unauthorized immigrants from deportation (the largest of which have since been put on hold by the course), 54 percent of Republicans told Quinnipiac pollsters that unauthorized immigrants should be required to leave the US.

It's been apparent for a while that immigration turns into a much more partisan issue when President Obama's name is involved. A 2013 Washington Post poll during the fight over the Senate bill found that Republican support for a path to citizenship for unauthorized immigrants dropped 21 percentage points — from 60 percent to 39 — when it was identified with the president. At the time, this was a much bigger gap than other hot-button issues like gun control, which presumably were already polarized. But it looks like immigration has become such a politically polarized issue that, even without mentioning particular politicians, many Republicans have decided to reject any possibility of allowing unauthorized immigrants to stay.

The problem: Mass deportation is an impossible policy that pretty much no Republican elected official can support

If this trend is legit, there is now a chasm between where the Republican base and the rest of America are on immigration reform. (As a whole, a majority of Americans — 56 percent in the CNN poll — continue to support legalization for many unauthorized immigrants.) That's definitely a problem for getting comprehensive immigration legislation passed in Congress. But it's a much more urgent problem for any Republican politician, because his constituency is increasingly committed to a position that it's going to be extremely difficult for him to endorse.

If mass deportation were a workable solution, someone would have put out a policy proposal by now. The problem is that it isn't. There's no reason to assume immigration agents could even find all 11 million unauthorized immigrants in the US — a majority of whom have lived in the US for more than a decade. And if they could, deporting all of them would cost about $50.3 billion — not to mention the additional costs (economic and otherwise) associated with splitting apart millions of families with US-born children and unauthorized parents.

In lieu of mass deportation, the most hardcore immigration hawks endorse the "attrition through enforcement" strategy popularized by Arizona's 2010 immigration law SB 1070. But "attrition through enforcement" doesn't appear to be effective in getting unauthorized immigrants to leave the US. And it's definitely not clear that it's enough to satisfy a Republican electorate that's increasingly convinced the US needs a plan to deport the immigrants who are already here.

This is, of course, above and beyond the political problem: Republicans are already underwater among Latino voters, and it's going to be much harder for them to win the White House if they don't improve their Latino support. As Republican members of Congress have shown over the last few years, they don't care enough about the GOP's presidential prospects to set their immigration agenda with that strategy in mind. But base support for mass deportation isn't just a problem for Republicans who want to get elected president — it's a problem for any Republican who actually wants to turn his or her party's preferences into law.