I'm the first to admit to a "survivor" bias. If an incumbent has survived a serious challenge or two -- especially in an unfavorable political environment -- I assume no challenge is too tough. But that's a dangerous assumption to make about even the hardiest Republican House incumbents this year.
On top of the obvious troubles -- such as a serious fundraising disadvantage for the National Republican Congressional Committee and the unprecedented number of voters who say they want Democrats in charge of Congress -- they also face new and unforeseen dangers.
Here's the big one: No one can figure out just how many new or non-chronic voters are going to show up on Election Day.
One facet of this is the so-called "enthusiasm gap." The latest Diageo/Hotline poll showed that while 60 percent of Democrats said they'd vote "enthusiastically" for Barack Obama this fall, just 46 percent of Republicans said the same about John McCain. To be sure, this shouldn't be taken to mean Republicans are going to stay home and Democrats are going to flood the polls, but it does suggest a turnout dynamic that these GOP incumbents have never seen before.
Then there's the difficulty of reaching the under-30, cell-phone-only set. For a Republican whose district houses universities or colleges, student turnout may no longer be a nominal concern.
But for a closer look at what's at stake for the survivor caucus, take Chris Shays of Connecticut and Mark Kirk of Illinois.
Shays and Kirk sit in decidedly Democratic districts, Shays bordering New York on Long Island Sound and Kirk on the North Shore along Lake Michigan. They win because they have compiled moderate voting records and established profiles that fit their district. It's tough to peel away voters who have supported these Republicans for years, even as those same voters have supported Democrats for president or statewide office. But add a bunch of new voters -- voters who don't have any such relationship or even the slightest knowledge of their record -- and it's easy to see how those voters could simply pull the lever for the candidate labeled with a "D."
The same goes for someone like Rep. Steve Chabot of Ohio. He's been on national Democrats' target list forever, and yet they've come up short every time. Still, it's easy to forget that this suburban Cincinnati district is almost one-third black. Having Obama on top of the ticket is an advantage that no other Democrat has ever had.
Rep. Jon Porter's suburban Las Vegas district was drawn to benefit Democrats, but he's held on against serious (though often severely flawed) challengers every year since 2002. Even so, getting known in such a transient district is tough, even for an incumbent who spends millions of dollars every other fall on TV. Now, there's the added trouble of sitting in a state that Democrats have staked out as a White House battleground.
Take a look at the registration rolls in Porter's district. In January, Democrats had a 10,000 voter registration advantage over Republicans. By May, that advantage had doubled to over 20,000. Longtime Nevada political analyst and columnist Jon Ralston wrote that this swing district has "swung decisively to the Democrats." To be sure, Porter's Democratic opponent, former Senate and gubernatorial nominee Dina Titus, has political baggage. But Porter can't assume these newly engaged voters know anything about it.
To be sure, all of these survivors know the difficult road ahead of them. That sounds like a cliche, but it's actually an important distinction. In an environment as ugly as this one, a well-prepared incumbent can still lose. But for untested incumbents -- those who haven't had a serious race in years, if ever -- and those with serious flaws, this environment is almost sure to be fatal. That's why Republicans Randy Kuhl of New York and Marilyn Musgrave of Colorado, two incumbents who have high negative ratings, can lose even though their districts are much safer than those of Shays, Kirk, Chabot or Porter.
Finally, keep an eye on the generic ballot test question. It's often a lagging indicator of voter sentiment, since voters don't start to pay attention to congressional contests until closer to November. Today's 10-to-15-point advantage for Democrats may not hold up if voters no longer see a vote for a Republican in Congress as a referendum on President Bush.