Democrats can’t blame this one on Rasmussen.  The National Journal polled 1200 adults nationwide to determine whether they would vote for Barack Obama’s re-election based on his first-year performance.  In a stunner, 50% said they’d vote for “someone else,” while only 23% said they would definitely vote for Obama:

A year into his tenure, a majority of Americans would already vote against Pres. Obama if the ’12 elections were held today, according to a new survey.

The Allstate/National Journal Heartland Monitor poll shows 50% say they would probably or definitely vote for someone else. Fully 37% say they would definitely cast a ballot against Obama. Meanwhile, just 39% would vote to re-elect the pres. to a 2nd term, and only 23% say they definitely would do so. …

But as GOPers focus on taxes and spending, that message seems to be causing Obama the most harm. Among those who believe Obama’s policies have moved the country in the wrong direction, 45% cite spending and government regulation as a top cause for their opposition.

These results are doubly bad.  Obviously, having half the country say they’d vote for a generic opponent isn’t good, but the sample type is the most Democrat-friendly a pollster can use.  “Adults” generate more left-leaning results than registered voters, and especially with likely voters.  If Obama can’t do better than 39% among adults, he is in deep trouble — and so are Democrats running in this year’s midterms.

The sample itself seems rather reasonable.  The partisan split is in the ballpark, with Democrats and independents a +5 over the GOP.  Twelve percent called themselves a “something else,” which seems rather high for the fringe parties even in the aggregate.  Eighteen percent of the respondents didn’t vote in the 2008 presidential campaign, and 4% said they voted for someone other than Obama or John McCain, which again seems a little high.   The two main-party candidates got 98% of the total popular vote in November 2008.  The difference could be people who don’t want to acknowledge their Obama vote rather than a sampling problem, however.

On health care, Obama lost ground in the last four months.  Nat’l Journal had net support in September at almost-majority level, 49/42.  Opposition has now moved ahead, 44/46.  Strong opposition and support were in a virtual dead heat in September, but 35% have strong opposition now to ObamaCare, while only 22% strongly support it.

The poll has another big red flag for Democrats.  After a year of single-party governance, Americans have grown very disenchanted.  In April of last year, 47% of respondents thought the country was moving in the right direction, against 42% who thought it was going off the rails.  Now, 55% think the country is moving in the wrong direction, and only 34% think otherwise.  Since only Democrats have been doing the driving, that gives a strong indication that they may find themselves replaced at the wheel at the next opportunity.