Palin, Biden Head to St. Louis for 2008's One-and-Only Vice Presidential Debate

— -- Heading into tonight's vice presidential showdown in St. Louis, an ABC News/Washington Post poll released today reveals the Sarah Palin boom has all but busted.

Watch the Vice Presidential Debate -- ABC News Live Coverage Begins at 9 p.m. ET

In his analysis, ABC News' Polling Director Gary Langer writes, "Skepticism about Sarah Palin has soared since she entered the national political stage, with six in 10 Americans now doubting her qualifications for office and fewer than half convinced of her grasp of complex issues."

Rick Klein, author of 'The Note', calls tonight's match-up "a face-off of a peculiar sort". (Rick will be live-blogging tonight throughout the debate.)

On Good Morning America Thursday, ABC News' Chief Washington Correspondent George Stephanopoulos said the debate stakes are high for the Alaska governor tonight and blogged, "Any mistake or gaffe by Palin could be fatal with a new poll finding voters are now questioning their commitment to Republican presidential candidate John McCain because of her."

Also on Good Morning America, ABC's Kate Snow previewed the preparation efforts of both candidates.