A month ago, a U.C.L.A. graduate student named Emily Elkins spent hours roaming a Tea Party rally on the Washington Mall, photographing every sign she saw.

Elkins, a former CATO Institute intern, was examining the liberal conceit that Tea Party marches are rife with racism and conspiracy theorizing. Last week, The Washington Post reported on her findings: just 5 percent of the 250 signs referenced Barack Obama’s race or religion, and 1 percent brought up his birth certificate. The majority focused on bailouts, deficits and spending  exactly the issues the Tea Partiers claim inspired their movement in the first place.

The easy thing would be to take them at their word. But for liberals, that would be too simple. The Democrats are weeks away from a midterm thumping that wasn’t supposed to happen, and the liberal mind is desperate for a narrative, a storyline, something to ease the pain of losing to a ragtag band of right-wing populists. Something that explains the Tea Parties  and then explains them away.

The “Tea Partiers are racists” theory is the most inflammatory storyline, but there are many more. Let’s consider them, in order of increasing plausibility:

THE TEA PARTIES ARE DRIVING REPUBLICANS OFF A POLITICAL CLIFF. This has been a common assumption since the Tea Parties first sprang up, and in some cases  Christine O’Donnell; Carl Paladino; and Rich Iott, the Nazi re-enacting House candidate  it has been vindicated. But just as often, the Tea Parties have elevated smooth-talking, eminently electable candidates, from Pat Toomey in Pennsylvania to Marco Rubio in Florida and Ken Buck in Colorado.