This could be a significant development in a very close race. And it almost certainly will affect the outcome in PA, MI, and OH.
Barack Obama's level of support among voters who preferred Hillary Clinton during the primaries is exactly where it was in June according to a new AP poll:
Before we get too excited I should point out that looking at this situation historically, most of these Democrats will indeed come home and support Obama on election day. However, even a 2-3% difference between history and what actually happens on election day could be huge for McCain. Unless the economy goes into a full scale meltdown, such a turn of events will almost certainly lock up Ohio for the Republican and give him a fighting chance in Pennsylvania. Most of these reluctant Hillary Democrats are older and Pennsylvania has the third highest percentage of voting seniors in the country.
An Associated Press-Yahoo! News poll shows that among adults who backed his rival during their bitter primary campaign, 58 percent now support Obama. That is the same percentage who said so in June, when Clinton ended her bid and urged her backers to line up behind the Democratic senator from Illinois.
The poll shows that while Obama has gained ground among Clinton's supporters - 69 percent view him favorably now, up 9 percentage points from June - this has yet to translate into more of their support.
In part, this is because their positive views of Republican presidential nominee John McCain have also improved during this period. Those supporting McCain have also edged up from 21 percent to 28 percent, with the number of undecided staying constant, the survey showed.
Clinton backers' reluctance to support Obama helps explain why he is having a tougher time solidifying partisan supporters than McCain. Overall, 74 percent of Democrats say they will vote for Obama, compared to 87 percent of Republicans behind the Arizona senator. About nine in 10 Clinton supporters are Democrats.
Florida too may be taken off the table if just a small percentage of Hillary voters go for McCain. What this means is the longer the holdout by these voters, the less McCain has to spend in FL and Ohio which means more resources for Pennsylvania. And the way things are looking in the midwest and west - McCain trailing in several key states that went to Bush in 2004 - many analysts believe that McCain is going to need Pennsylvania to win in order to overcome Obama's flipping a couple of red states to blue.