Conservatives are outraged about the situation on the U.S.-Mexico border -- so much so that it might even be hurting the already-dim future prospects for comprehensive immigration reform.

Republican support for allowing undocumented immigrants to stay in the United States legally has dropped by 10 points since February, according to a new poll from the Pew Research Center.

While 64 percent of Republicans back then supported allowing immigrants to stay in the United States legally -- a key aspect of comprehensive reform -- only 54 percent do today. Support has also dropped for Democrats and independents, but by much smaller margins.

The biggest drop in support for giving undocumented immigrants legal status was with tea party Republicans. In February, 56 percent thought undocumented immigrants should be allowed to stay if they met certain requirements. Now, only 41 percent agree with that statement.

Why does this matter? Well, the big hold-up in the whole immigration debate remains the internal split in the GOP between party leaders who want to get something done and conservatives who are worried about granting "amnesty." This poll suggests that split is close to 50-50 again -- and the party couldn't even get anything resolved when the legalization crowd was the clear majority.

It's not totally clear that the drop is related to the situation on the southern border, but that's certainly the most obvious prospect.

The fact is that the fate of undocumented immigrants has become a far more visible -- and partisan -- issue in the past month. With the debate over what to do with the unaccompanied minors coming to the border from Central America mounting, Americans are tuning in much more and seeing what their respective side thinks. And many Republicans have been pushing for a quicker deportation process for these undocumented children.

Americans are also less than supportive of how President Obama has handled the situation. Twice as many disapprove (56 percent) as approve (28 percent). Conservative leaders have been arguing for weeks that the situation on the border effectively eliminates any trust Republicans might have had in Obama to faithfully and competently implement comprehensive reform.

We already knew immigration reform was dead for this Congress, but it's prospects for the next Congress are at stake too. And it's not looking good.

But although Republicans appear to be turning away from legalization, and even Democrats and independents are less enthusiastic than before about letting undocumented immigrants stay, that hardly means that the country is ready to endorse the Republican Party's entire platform on immigration.

The poll shows that Americans aren't quite sure whether they trust Republicans or Democrats more when it comes to immigration.

While the country trusts Republicans more on the economy, and trusts Democrats more on abortion and contraception, trust on immigration is within a margin of error (42-40 in the GOP's favor).

Americans are willing to be persuaded on this issue, right at the moment when crisis has forced both parties to make big decisions on immigration. Whichever party Americans end up giving their trust on immigration to could depend completely on how they grade the resolution to the undocumented minor debate -- and whom they end up blaming or rewarding.

What's perhaps most interesting, though, is that even as support for legalization has dropped, Americans are demanding some kind of legislation more than before.

All political affiliations have seen their support of passing "significant" immigration reform increase dramatically. The question does not ask what kind of legislation respondents would like to see -- "significant" could include little more than border security, for example -- but it's obvious that Americans want to see something.

Americans want to see something. Most of them aren't sure quite what. Everyone's at least moderately supportive of a policy change that would allow undocumented immigrants to stay -- but far less than they used to be.

And the fact that Republicans are less on-board with legalization than before spells bad things for comprehensive immigration reform going forward.