Jonathan Bernstein at the Washington Post issued an advisory this week to journalists covering immigration legislation in the House. Due to the squirrelly nature of the politics within the Republican caucus, he wrote, reporters can't take at face value all Republican Party opposition to immigration reform.

It may be the case that a fair number of Republican members want a bill to pass -- but without their votes. They may believe that the bill is good for Republicans in general but not in their districts; they may even believe that their own long-term prospects are better with an immigration bill in place but that their short-term prospects could be endangered if they support it.

If that’s the case, however, those members who support passing the bill but don’t want to vote for it are certainly not going to want reporters to print that; for the record, they may even be among those who denounce “amnesty” the loudest.

This situation is not unique. Legislators sometimes vote their consciences, other times their districts and most of the time their party. Once in a while, on gay rights or National Institutes of Health funding, for example, they may even vote their family member.

But on what will almost certainly be the most high-stakes vote of this Congress, voting one way while hoping another is risky for two reasons.

First, political dynamics may enable hypocrisy but they don't always reward it. There will be -- already are -- Republicans who genuinely, loudly oppose "amnesty" for the estimated 11 million undocumented immigrants in the U.S. If those voices characterize the Republican stance, and that stance is seemingly confirmed by a majority of Republicans voting against the bill, the party may find itself deeper in its demographic trench -- even if reform passes.

I suppose it's possible that Democrats would not herald their support for legalization -- and the Republican opposition to it -- all over Univision, Telemundo and other Hispanic media. But given the obvious political benefits, that seems highly unlikely. So rather than enabling Republicans to escape their demographic dilemma, reform might reinforce it for at least a couple of elections.

Second, if many Republicans feel compelled to denounce the legislation, the cost of voting in favor could rise for all Republicans -- and possibly even for some Democrats. Voters don't follow complicated legislation very carefully. (Given the state of public knowledge of the Affordable Care Act, that is a vast understatement.) If voters hear a lot of doomsday rhetoric coming out of the House, support for reform could erode, making a majority more difficult to muster.

Engineering majority support for immigration reform with only 20 or 30 votes from Republicans will be complicated enough for Speaker John Boehner. Achieving that outcome while stifling the outbursts of anti-immigration Republicans will be tough indeed. And a majority of Republican voters remains cool to key elements of reform, such as legalization.

Most pundits and immigration experts seem to think reform will become law. I suspect they're probably right. But the House is not an organized legislative body; it is bedlam. Much simpler, less volatile votes have gone awry there. If the wild ones have the run of the place, all bets are off.

(Francis Wilkinson is a member of the Bloomberg View editorial board. Follow him on Twitter.)