Obama, meanwhile, continues to lead in trust to handle the economy, 50-39 percent, and it's the No. 1 issue by a larger-than-ever margin. Forty-three percent volunteer it as the most important issue in their vote, a high level of agreement on an open-ended question. Fourteen percent cite the Iraq War -- continuing a downward path since last fall, when it dominated the agenda -- with all other "top issue" mentions in the single digits.
Obama also leads in trust to handle social issues such as abortion and gay civil unions, albeit by a smaller margin than last month, and has a slight edge on energy policy. The two are ranked evenly on Iraq and taxes, and McCain's improved on immigration policy.
McCain does slightly better on consistency, but Obama continues to lead him on a variety of other personal attributes: Would stand up to special interests, 53-32 percent; understands the problems of people like you, 49-36 percent (a bit less of a margin than last month); would work in a bipartisan way, 49-37 percent; and best represents your personal values, 50-43 percent. They're close on "stronger leader" -- 49-44 percent, Obama-McCain, an improvement for Obama -- and run evenly on who's more honest and trustworthy.
Obama's single biggest advantage is on being seen as "more optimistic," a 64-28 percent lead over McCain and a potentially important one, given the generally better performance of sunnier candidates. Additionally, 48 percent say McCain has spent more time attacking his opponent than addressing the issues; fewer, 29 percent, say Obama has mainly spent his time going negative.
As noted, a substantial 45 percent say they're uncomfortable with the notion of McCain taking office at age 72, including 20 percent who are entirely uncomfortable with it. Far fewer express discomfort with the idea of Obama becoming the first African-American president -- 11 percent, with 6 percent entirely so.
Regardless of popular buzz about various groups du jour, there are few true swing voter groups; they include independents, white Catholics and, arguably, married women. Among two of them the race is close: Among registered voters, independents divide by 45-43 percent between Obama and McCain; married women, 48-44 percent.
But there's a wider gap -- a 50-39 percent McCain advantage -- among white Catholics. That should be disconcerting to the Obama campaign, since white Catholics have voted for the winner in each of the last eight presidential elections. And even in the absence of data demonstrating that affinity with a vice presidential nominee moves votes, it could suggest one possible line of thinking in Obama's camp: Biden is Catholic.
Among whites overall, McCain has a scant 49-43 percent edge; Bush won whites by wider margins in 2004 and 2000 alike. Obama's winning support from 88 percent of blacks -- customary for a Democratic presidential candidate -- and six in 10 Hispanics.
There's a pronounced gender gap in the contest, with a 50-41 percent McCain advantage among men, but a wider 55-37 percent Obama lead among women (better than Kerry's in 2004). Indeed Obama leads among white women, 50-42 percent (Kerry lost them), while McCain has wide a 57-35 percent advantage among white men. Women are more apt than men to be Democrats.