As polls have consistently shown, Americans aren't big fans of Congress. Yet whenever elections roll around, voters rarely replace their representatives with fresh faces.

Last year, 90 percent of House incumbents won re-election, according to OpenSecrets, despite polls pegging Congress' approval rating at around 20 percent heading into Election Day. In 2004, voters sent fully 98 percent of incumbents back to Washington even though a majority said they disapproved of Congress' job performance.

A Gallup poll released Thursday sheds some light on this seemingly paradoxical phenomenon. It found that, while Americans strongly dislike Congress as a whole, they generally like their own representatives. 

In the survey, just 16 percent of respondents said they approved of the job Congress is doing, versus 79 percent who said the opposite. That's in line with other recent polls that have found Americans pretty down on Congress. Two April surveys from CBS/New York Times and Fox News both pegged Congress' approval rating at a meager 17 percent.

At the same time though, Gallup found that a 46 percent plurality of Americans approve of the job the representatives from their districts are doing, versus 41 percent who said they disapproved. Digging deeper, Gallup found that individual lawmakers got higher marks if respondents could first name them and their party affiliation. Of those who knew both name and party, 62 percent said they approved of their representative, while 32 percent said they did not.

So what's causing this divergence?

Here's Gallup with some possible explanations:

Paradoxically, many Americans actually approve of the job their own district's congressional representative is doing. And those who say they know the name of their representative are even more likely to be positive about that individual's work. This may involve basically nonlegislative ways representatives benefit their districts, such as helping their constituents deal with the federal bureaucracy or bringing federal money back to the district to fund projects that benefit the local economy. Also, in an era when district borders are often drawn specifically to benefit one of the parties, many representatives are likely to be politically in tune with their districts. 

Thus, when thinking about Congress as a whole, Americans are nearly as sour as they have ever been, but when they think just about their own representative, they feel much better about the job that person is doing. [Gallup]

That helps explain why incumbents do so well, even when Congress as a whole is less popular than, say, cockroaches or Nickelback.