The number of McCain supporters who describe themselves as "very enthusiastic" about his candidacy rose 18 points to 46 percent after his convention. Today it's subsided to 34 percent, while a steady and far greater number of Obama's supporters remain very enthusiastic about their candidate, 62 percent.
In a related challenge, concern about the candidates' age is up -- 48 percent, a new high, call it an important factor in their vote, and it hurts McCain: Those who call it important favor Obama by 2-1, 63-32 percent, compared with a 12-point McCain advantage among those who don't see his age as an issue.
Far fewer -- 16 percent, a new low -- say race is an important issue, and that view does not meaningfully impact vote preferences.
Then there are white women.
They've been a changeable group this year, shifting, for example, from +7 Obama to +11 McCain among likely voters from late August (before the conventions) to early September.
They're back to a dead heat now, precisely where they were in mid-July. But the fact that they've backed McCain by as much as a 16-point margin (in June) keeps them a group to watch.
There are other significant changes in key swing voter groups -- so identified because their allegiance swings and they're big enough to make a difference.
White Catholics have shifted from a broad post-convention preference for McCain, 57-38 percent, to a dead heat.
Independents, likewise, from +10 for McCain two weeks ago to +14 for Obama now. And married women, +11 for McCain Sept. 7, are +5 for Obama now.
Among other changes, a swing to McCain in the Midwest -- a 54-43 percent McCain advantage Sept. 7, also has been reversed; Obama's now up there, 53-40 percent.
More change is entirely possible.
Seventeen percent of likely voters remain movable, meaning they haven't definitely made up their minds. And movability peaks among some of the swing groups that indeed have been moving: Twenty-eight percent of white Catholics, 25 percent of independents and 23 percent of Midwesterners are movable. Some of their numbers have changed preferences; some well could again.
Swing groups, however, haven't been the only ones to move.
There also have been sharp changes in voter preference among other groups, including postgraduates, independent women and non-evangelical white Protestants. And it's tightened among white men as well – 54-40 percent for McCain, compared with 62-34 percent after the conventions.
Among election issues, the economy is in the driver's seat.
A near-unanimous 91 percent of likely voters say it's in bad shape -- not so good (33 percent) or poor (58 percent). The distinction matters: Among those who say the economy's merely not good, McCain leads by 61-34 percent. Those who say it's poor favor Obama, 69-26 percent.
Other economic views cut similarly. Among people who say the economy's the most important issue, Obama leads by 61-35 percent; their rising number, again, boosts him. Among those who pick all other issues combined, McCain leads, 54-42 percent.