We've written many times on this blog about the fact that Republicans in Congress have very little incentive to come to the middle on the big issues before the country.

And a new poll from the Pew Research Center says it all: Quite simply, it's because the GOP base demands principles over compromise.

According to the new national Pew survey, 50 percent of Americans would rather that their elected officials "make compromises with people they disagree with" rather than "stick to their positions" (44 percent).

But when you break it down by party, you see the reason we have gridlock.

While 59 percent of Democrats prefer compromise to principled stands, just 36 percent of Republicans say the same (compared to 55 percent who want principled stands).

For Republicans, that's actually up slightly from the 32 percent who wanted compromise two years ago, after the 2010 election in which the GOP reaped huge gains by standing resolutely against Obama's agenda. But over the same span, the percentage of Democrats calling for compromise has risen significantly -- from 46 percent to 59 percent. And independents have also moved by double digits toward favoring compromise.

In a lot of ways, the tea party (whose principles live on even as the movement has waned) was a response to this impulse by the GOP base. And it's success in a number of primaries has sufficiently scared Republican incumbents, the vast majority of whom have more to fear in a primary than the general election, away from the political middle.

The problem for Republicans is that this has led to them becoming the party of obstruction -- at least in the eyes of the American people.

A new Washington Post-ABC News poll shows fully two-thirds -- 67 percent -- of Americans say the Republican Party does too little to compromise on important issues, while just 48 percent say the same of President Obama.

Whether or not you agree with the idea that Republicans are more unwilling to compromise than Obama and the Democrats, that's certainly the perception that exists today.

For Republicans, it seems, they are caught between a rock and a hard place. Their base demands that they resist compromise, but doing so causes the party as a whole to fall out of favor with the American public.

The Post-ABC poll shows 71 percent of Americans disapprove of the GOP, while 59 percent disapprove of the Democratic Party and 41 percent disapprove of Obama.

Under this set-up, there are really no easy answers for the GOP. If the party's lawmakers compromise more, they may gain favor with the political middle, but their base will resist -- and has resisted -- and they will risk their political careers. If they continue to make principled stands, they will likely win reelection, but their party's brand may remain, as GOP former congressman Tom Davis (Va.) famously said, the political equivalent of "dog food."

How and whether Republicans solve this riddle will say a lot about how they progress as a force in American politics.