Clinton backers still wary of Obama

Despite Hillary Clinton's repeated entreaties, her supporters are still not falling in behind former rival Barack Obama, according to a new poll released today.

And that reluctance is weakening Obama six weeks before Election Day, according to the poll conducted for the Associated Press and Yahoo News.

Among Clinton voters during the Democratic primaries, 58 percent now support Obama -- the same percentage as in June, when Clinton ended her bid and threw her support to Obama -- even though 69 percent view him favorably, up 9 percentage points from June.

Meanwhile, the share of Clinton supporters saying they'll vote for Republican John McCain grew from 21 percent to 28 percent, with the number of undecided staying constant, according to the survey, conducted by Knowledge Networks.

And while 87 percent of Republicans are behind their party's nominee, only 74 percent of Democrats say they will vote for Obama.

Clinton gave an impassioned speech praising Obama at the Democratic National Convention last month, then took the extra step of having delegates formally approve Obama's nomination. Over the weekend, she launched a grassroots effort to get her loyalists on board.