As more and more facts about the failed vote come out, it becomes plain that there was more going on than just Pelosi's ill-timed, ill-directed, screw bi-partisan cooperation, blame Bush speech.
The good of the nation took second-place to election year posturing and opportunism.
The democrats did not need Republican votes to pass this bill. All they had to do was whip all of their horses in line and the it would be a done deal. One reports alleges that democratic House members up for reelection in strongly contested races were urged to vote against the bill, because enough Republicans were committing to vote for it that it was safe to do so. Republicans got wind of the double-dealing. That, and Pelosi's speech had them livid with outrage.
Cynics might also state that the democratic presidential candidate morphed into the Invisible Man during the debate over the bipartisan bill at a time when his influence was sorely needed.