Obama's lead among single women, a core Democratic group, is similar to Kerry's in 2004, but he's doing better with single men, and especially with married men and women alike -- again, with the economy as the motivator.
While McCain's lead among whites is smaller than Republican margins in this group since 2000, Obama's advantage among blacks is larger -- near-unanimous 98 percent support, compared with Kerry's 88 percent and Al Gore's 90 percent. Obama also has a 70-28 percent advantage among Hispanics, a level unseen for a Democrat since 1996.
Obama and McCain run closely in this survey among working-class whites, those with less than $50,000 in annual income, 49-46 percent.
A bigger difference from 2004 is the narrowed gap among better-off whites. McCain leads among middle-income whites by 14 points; Bush won them four years ago them by 24. And McCain leads by just 8 points among upper-income whites, a group Bush won by 26 points.
Obama's attracting 11 percent of Republicans, compared with Kerry's 6 percent in 2004; those chiefly are moderate or the few liberal Republicans, among whom Obama's winning 24 percent, double Kerry's level. McCain's 9 percent of Democrats is more similar to Bush's 11 percent four years ago.
Obama also is supported by 20 percent of conservatives, ahead of Kerry's 15 percent; those chiefly include conservative Democrats staying with the party.
The large number of interviews in the tracking poll allows a look at some small groups.
One is Jews; just 2 percent of likely voters, they divide by 67-31 percent between Obama and McCain, the best for a Republican since George H. W. Bush's 35 percent in 1988.
Another group of some interest is the cell-phone only population, which ABC and the Post have been including in daily tracking. They're a broadly pro-Obama group, by 62-35 percent.
Indeed in landline-only interviews, the Obama-McCain race stands at 52-45 percent among likely voters. The inclusion of cell-only respondents makes it 53-44.
Finally there's the ground game.
Updating Monday morning's report, 28 percent of all likely voters say they've been contacted directly by the Obama campaign, 22 percent by the McCain side -- an Obama advantage, but for both sides tens of millions of personal contacts by both campaigns, in person or by phone, e-mail or text message.
Contacts are higher in the 18 battleground states and five-toss-up states (Florida, Ohio, North Carolina, Missouri and Indiana) as identified by the ABC News Political Unit.
McCain campaign contacts are reported by 34 percent in the battlegrounds and 35 percent in the toss-ups; Obama contacts, by 39 and 36 percent, respectively.
What matters, though, is not just the number of contacts but their targeting and/or effectiveness. Obama has a very large advantage nationally -- but one that shrinks somewhat in the battleground states, and disappears in the five closest.
As the table shows, nationally, among all likely voters who report a contact by the Obama campaign, 70 percent support him, while among those who report a McCain contact, 53 percent support him.
In the battleground states, Obama is supported by 66 percent of those who've been contacted by his campaign, McCain by 54 percent of those who've heard from him.
But in the five toss-up states, Obama is supported by 56 percent of his contacts, McCain by 60 percent of his. Maybe that's why they call them toss-ups.