Another day, another bill that the Democratic-run House narrowly passed even as many of the party’s most politically vulnerable members once again broke ranks.

This time it was Wednesday’s vote for a $290 billion increase in the federal debt ceiling, from $12.1 trillion to $12.39 trillion, so that the Treasury Department could continue borrowing. It passed 218-214, with 39 Democrats joining all Republicans in opposition.

What was striking about the vote breakdown was that the overwhelming majority of Democrats who voted no — 32 of 39 — are first or second-term members who represent districts that they wrested from Republican control. The GOP will be contesting many of these districts in what they expect will be a more Republican-friendly 2010 election midway through President Obama’s term.