Pollster Scott Rasmussen first reported that support for Barack Obama and the Democrats in general had begun to seriously slip over a month ago, especially on the economy.  At first, other pollsters didn’t catch the trend, but now almost all surveys show Americans losing confidence in the administration’s efforts on fiscal matters.  Now the bleeding also has begun on health care, as the new Washington Post poll shows:

Heading into a critical period in the debate over health-care reform, public approval of President Obama’s stewardship on the issue has dropped below the 50 percent threshold for the first time, according to a new Washington Post-ABC News poll.

Obama’s approval ratings on other front-burner issues, such as the economy and the federal budget deficit, have also slipped over the summer, as rising concern about spending and continuing worries about the economy combine to challenge his administration. Barely more than half approve of the way he is handling unemployment, which now tops 10 percent in 15 states and the District.

The president’s overall approval rating remains higher than his marks on particular domestic issues, with 59 percent giving him positive reviews and 37 percent disapproving. But this is the first time in his presidency that Obama has fallen under 60 percent in Post-ABC polling, and the rating is six percentage points lower than it was a month ago. …

Since April, approval of Obama’s handling of health care has dropped from 57 percent to 49 percent, with disapproval rising from 29 percent to 44 percent. Obama still maintains a large advantage over congressional Republicans in terms of public trust on the issue, even as the GOP has closed the gap.

The erosion in Obama’s overall rating on health care is particularly notable among political independents: While positive in their assessments of his handling of health-care reform at the 100-day mark of his presidency (53 percent approved and 30 percent disapproved), independents now are divided at 44 percent positive and 49 percent negative.

Bear in mind that this poll has a rather odd partisan split.  Unlike the CBS poll, which got deliberately tweaked to emphasize Democrats, this poll appears to have a natural sample that overemphasizes independents.  According to the raw data, the poll only has 22% Republicans, 33% Democrats, and 41% independents.  In that case, Republicans are significantly undersampled, and Democrats slightly undersampled.  The independents lean slightly Democratic, which was certainly true in the last election, but the double-digit gap between Democrats and Republicans didn’t exist in the presidential election and certainly doesn’t reflect the electorate — and this sampling bias still can’t mask the decline Obama has seen in his polling.

One of the most interesting questions in which this can be seen is in question 15: Is Obama a new-style Democrat who will be careful with the public’s money, or an old-style tax-and-spend Democrat?  Obama still gets a majority saying new-style Democrat, 52%-43%, but that metric shows a lot of erosion.  Four weeks ago, that was 58%-36%, and four months ago 62%-32%.  Trending on Obamanomics is also heading south.  Confidence in its ability to improve the economy has fallen to 56%-43%, down from 64%-35% in March.

However, as the Post reports, the most remarkable numbers come from the trendline on health care.  In April, Obama had a 57%-29% approval-to-disapproval rating on this issue.  By June, it was 53%-39%, at about the time the CBO began scoring ObamaCare.  Now it’s at 49%-44%, almost within the margin of error, and that was before the CBO rated the House version of ObamaCare as a deficit buster.

Obama will hold another prime-time press conference on Wednesday to try to sell ObamaCare to the nation.  These numbers show why he’s going back to the well, but they also show that he’s rapidly losing credibility.  More jawing at the cameras may not help much.