The problem for Republicans is that while the Bush coalition is broader than its opposition, it is not nearly as firm. Thus, when the support of Bush voters falters, liberal Democrats are fully prepared to make the most of it. This was a key factor in the undoing of the GOP’s congressional majority in 2006. Gore/Kerry voters were strongly opposed to George W. Bush as early as 2003. Intensity, however, is not enough in elections where everybody gets one vote, so Bush and the Republicans could hold the line. But when the war effort slipped, the Bush coalition weakened, and its highly motivated opponents were there to seize the advantage.

Unfortunately for the Republicans, something like this happened in the Nevada and Colorado Senate races last week, where Democrats Harry Reid and Michael Bennet hung on by slender margins. These are both states that George W. Bush carried twice. This year, the Republicans won the popular vote for the House in both states, but lost critically important Senate contests. The reason was terribly weak candidates whom the Democrats successfully labeled as extreme. This was sufficient to scare just enough of the Bush vote away to deliver victory to the Democrats. In both Nevada and Colorado, the county by county returns tell exactly the same story: The Democrats’ firm bases came in strong, while the Republican-leaning areas did not lean Republican enough. Even though President Obama’s job approval was negative in both states, his allies won reelection to the Senate…

The lesson here is that, while the Bush coalition remains a potential majority alliance, it is an unstable one. It requires a solid messenger, one whose appeal is too broad for him or her to be damaged by the Democrats’ predictable accusation of extremism. Republicans need to bear this in mind as they begin to deliberate over the party’s nominee for president in 2012. They need to ask themselves whether each contender is sufficiently conservative to be a good steward of both the government and the Republican brand, but they also must ask whether each can articulate the conservative message in a way that resonates with a broad cross-section of the American people.