An announcement bump for Mitt Romney and a bus-tour boost for Sarah Palin put the pair atop the field for the Republican presidential nomination. But while their primary standings are similar, their broader prospects for election look vastly different.

Romney appears formidable: In a general-election trial heat in the latest ABC News/Washington Post poll he runs evenly with Barack Obama among all Americans, and numerically outpoints him, 49-46 percent, among registered voters -- not a statistically significant lead, given sampling error, but a clear reflection of Obama's vulnerability to a well-positioned challenger.