The power of incumbency reigns. However, if you’re a Democrat you constituents are more likely to vote you out compared to Republicans in a NPR congressional battleground pool. From NPR:
To gauge what voters are thinking in House districts where surveys show the races will likely be tight in November and a switch in party control is possible, Democratic firm Greenberg Quinlan Rosner Research and Republican firm Public Opinion Strategies conducted a poll of 1,200 “likely” voters in 60 battleground districts that elected Democrats in 2008 (one of the seats is vacant) and 10 districts now represented by Republicans. The full poll, including the list of battleground districts, is here.
Do you approve or disapprove of the way [your incumbent House representative] is handling [his or her] job as a member of the U.S. Congress? (Skipped if open seat)
Margin of error: +/- 3.5 percentage points
Do you think you will definitely vote to re-elect [your incumbent House representative] to Congress, probably vote to re-elect [your incumbent House representative], probably vote for someone else, or definitely vote for someone else? (Skipped if open seat)
Democrats only four and half months to get their act together or a landslide will overtake them.
NPR has the rest of the story.