Washington ? Barack Obama’s support from backers of Hillary Rodham Clinton is stuck smack where it was in June, a poll showed Tuesday, a stunning lack of progress that is weakening him with fellow Democrats in the close presidential race.

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. The share of Clinton supporters saying they’ll vote for McCain edged up from 21 percent to 28 percent, with the number of undecided staying constant, according to the survey, conducted by Knowledge Networks.

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 with 87 percent of Republicans behind the Arizona senator. About nine in 10 Clinton supporters are Democrats.

The problem that supporters of Clinton, the New York senator, have with Obama seems to flow from their measure of him as a candidate, not from issues. From establishing a timeline for a U.S. withdrawal from Iraq to abortion to canceling tax cuts on the rich, their views of the importance of issues are virtually identical to Democrats in general.

Yet they find Obama less likable, honest, experienced and inspiring than Democrats overall do, and they have a better view of McCain. And while majorities of Clinton supporters say Obama shares their values and understands ordinary Americans, they’re less likely to say so than Democrats overall.

“It’s just a gut feeling, my gut tells me he’s not it,” Leslye Burgess, 53, a federal Treasury Department manager and Clinton supporter from Fairfax, Va., said of Obama.

The GOP’s selection of Sarah Palin as McCain’s running mate has had no net impact on Clinton loyalists – a group Republicans were hoping to lure by picking the Alaska governor.

Twenty-one percent in the poll said Palin on the ticket makes them likelier to back McCain, 21 percent said it makes them less likely, and 58 percent said it had no impact.

The choice of Joe Biden as Democratic vice presidential candidate makes them a bit likelier to vote for Obama, but seven in 10 said it didn’t matter.