Mitt Romney has solidified his position for the Republican nomination but lost ground in the main event, with improved economic indicators and questions about Romney's wealth and taxes lifting Barack Obama to a head-to-head advantage for the first time this cycle.

Fifty percent of Americans in this new ABC News/Washington Post poll approve of Obama's job performance, the most since spring. Fifty percent say he deserves re-election, better than Bill Clinton at the start of his re-election year and as good as George W. Bush a month before he won a second term. And Obama now leads Romney among registered voters by a slight 51-45 percent, the first time either has cracked 50 percent in a series of matchups since spring.

Two chief factors are at play. One is the economy's gradual but unmistakable improvement, marked by the newly reported January unemployment rate of 8.3 percent, the lowest since a month after Obama took office. The president's approval rating on handling the economy, while just 44 percent, is its best in 13 months.

The other: questions focused on Romney's wealth, his low tax burden and, relatedly, his ability to connect with average Americans. Notably, 52 percent in this poll, produced for ABC by Langer Research Associates, say the more they hear about Romney the less they like him - double the number who like him more.

Based on his roughly 14 percent tax rate on 2010 income of about $22 million, the public by a broad 66-30 percent says Romney is not paying his fair share of taxes; even nearly half of Republicans say so, as do half of very conservative Americans. The public by 53-36 percent, a 17-point margin, thinks Obama better understands the economic problems people are having. Obama leads Romney by 55-37 percent in trust to better protect the interests of the middle class, and remarkably, by 10 points, 52-42 percent, in trust to handle taxes.

While the situation may be unusual given Romney's particular wealth- and tax-related vulnerabilities, competitiveness on taxes can be a telling indicator. Mike Dukakis, Al Gore and John Kerry trailed on taxes in 1988, 2000 and 2004, and lost. Clinton and Obama led on taxes in 1992 and 2008, and won. (The record's not perfect; Clinton trailed on taxes in 1996, and won anyway.)

SCRIPT - Each election follows its own script, and there's time aplenty for 2012's to play out. Romney may be in a weakened position given the internecine GOP primaries, Obama in a better one given improved economic data and his well-received State of the Union address. Among Americans who've heard or read about his address, 57 percent approve. Far fewer, 36 percent, approve of what they've been hearing from the Republican candidates overall.

But it's true too that Romney's fortune - if elected he'd be one of the wealthiest presidents in history - is a delicate issue given the public's long-running economic discontent. Sixty-eight percent think the tax code favors the wealthy in this country; 56 percent feel that way strongly. Seventy-two percent favor raising taxes on millionaires; 59 percent say so strongly. Both include majorities of Republicans.

Life, though, is hardly more comfortable for Romney's top opponent, former House Speaker Newt Gingrich. He trails Obama by 54-43 percent among registered voters. And while Obama's majority support against Romney is new, the president has held a majority against Gingrich in four out of five ABC/Post matchups since spring.

Moreover, while Americans by 52-24 percent like Romney less, rather than more, as they learn more about him, they say the same about Gingrich even more broadly, by 60-19 percent.

GOP RACE - In the GOP contest, among Republicans and Republican-leaning independents, Romney leads Gingrich by a substantial margin, 39-23 percent, with 16 percent for Rick Santorum and 15 percent for Ron Paul. (It's very similar when winnowed to registered voters, 38-24-18-14 percent.)

Despite his loss to Gingrich in South Carolina, 71 percent of leaned Republicans expect Romney to win the nomination, essentially the same as in mid-January, a week before that primary. And drop-outs may not make a difference: Those who don't support either Romney or Gingrich now divide about evenly between them as their second choice, 41 percent to 37 percent.

Romney, though, is not without challenges in his own party's nominating process. Electability remains his standard; 56 percent of leaned Republicans pick him over his competitors as best able to defeat Obama in November. (Gingrich has improved by 12 points on this score, but only to 22 percent.) On others, though, Romney's numbers are far softer:

• Gingrich leads by a dozen points among leaned Republicans as having the best experience for the job, moving ahead of Romney on this quality after essentially an even split last month.

• All four GOP candidates run about evenly on who better "understands the problems of people like you" - Romney 23 percent, Gingrich and Santorum 21 percent apiece, Paul 18. That makes empathy a relative weakness for Romney within the GOP tent, as well as beyond it.

• Romney also only runs about evenly with one or more of his competitors on three other qualities - best representing core Republican values, standing up for his beliefs and honesty and trustworthiness. The latter, though, is especially weak for Gingrich; a mere 7 percent rate him as the most honest and trustworthy candidate, last on the list by a wide margin.

One other quality again works for Romney: Forty-three percent say he has the best personality and temperament for the job. That dives to 19 percent for Gingrich, with Santorum and Paul close by.

Ratings on issues tell a similar tale. Romney leads his competitors in trust to handle the economy, 14 points ahead of Gingrich. But they're much closer on both social issues and the deficit, with 7-point improvements for Gingrich on both.

Romney's support for the nomination is its best to date among "somewhat" conservatives, 43 percent, and mainline Republicans (as opposed to Republican-leaning independents), 41 percent. He remains much weaker among very conservatives and strong supporters of the Tea Party movement, with 25 percent support in both groups.

RELIGION - Romney, a Mormon, generally has struggled to win support from evangelical Protestants in the primaries (though he did better in Saturday's caucuses in Nevada), a result again marked in this survey: He leads Gingrich among non-evangelical white Protestants by 51-24 percent, yet among their evangelical counterparts Gingrich has 30 percent support, Romney and Santorum 27 percent each. It should be noted, though, that in a general-election matchup white evangelicals do side with Romney over Obama, 66-27 percent - and that's as good as Gingrich does against Obama in this group, 64-30 percent.

In another question, 38 percent of Americans say it's important to them that a candidate for president shares their religious beliefs; 62 percent say not. Uniquely among evangelical white Protestants - just fewer than two in 10 Americans overall - this flips: Sixty-eight percent in this group call it important to have a candidate who shares their religious beliefs, 32 percent not.

In the primary that helps Gingrich; in the general election, though, it helps Romney vs. Obama, but only among those who say shared religious beliefs matter "a great deal." Romney leads Obama in this group by 55-36 percent. Among all other Americans, though, Obama leads by a similar margin, 56-40 percent.

One further result finds that more people call Romney's religion a major reason to oppose him, 17 percent, than a major reason to support him, 4 percent - a net negative by 13 points, stretching to 22 points among evangelical white Protestants (25 percent negative, 3 percent positive). However, 77 percent of Americans overall, and 71 percent of white evangelicals, say it's not a major factor one way or the other.

POSITIVES and NEGATIVES - Romney's business experience overall is a substantial net positive for him; 48 percent call it a major reason to support him, vs. just 12 percent who call it a major reason to oppose him. Digging deeper, though, there are compunctions: The public divides evenly, 43-44 percent, on whether Romney's wealth is a positive (an achievement of the American dream) or a negative (a result of advantages others don't have).

There's a big income gap on this question. Among people with household incomes less than $100,000 a year, just 38 percent see Romney's success as an achievement of the American dream. Among those with higher incomes, this soars to 65 percent.

There's a division, as well, on his work buying and restructuring companies: Thirty-six percent think Romney cut more jobs than he created; 32 percent, created more than cut. The high number of undecideds makes this issue open ground for Romney and his opponents to contest.

For Gingrich, his work as speaker in the early 1990s is seen more as a major reason to oppose than to support him, 33 percent vs. 21 percent. Far more damaging are views of his work since leaving office as a consultant for companies with an interest in federal policy making: this is seen as a major reason to oppose rather than support him by 44-12 percent, net negative by 32 points.

Then there's Obama. His handling of the economy is a net negative, but by less than might be expected: Forty-seven percent call this a major reason to oppose him, 39 percent to support him, negative by 8 points. By contrast, his handling of the threat of terrorism is a broad net positive, by a 36-point margin.

OBAMA and ROMNEY/ ISSUES - There are continued challenges for Obama. A negative turn for the economy (watch gasoline prices) could be very damaging. His approval rating on creating jobs is flat this month at 44 percent. Just 38 percent approve of his handling of the deficit, while 58 percent disapprove, a serious weakness unless he can make the case that it was deficit spending that turned the economy. And fewer than half, 47 percent, approve of his handling of taxes, even if he's leading Romney on the issue.

On the key issues, handling the economy overall and creating jobs, Romney and Obama are running about evenly - 48-45 percent and 47-45 percent, respectively; and on the deficit Romney opens a 10-point lead, 51-41 percent.

But Obama has other strengths, beyond trust on the middle class and his advantage on taxes. Challenged for lack of foreign policy and military knowledge in 2008, both are strong for him now: He leads Romney by 56-37 percent in trust to handle international affairs and by a similar 56-36 percent in trust to handle terrorism, two points he's likely to stress in the campaign ahead.

Obama faces a record partisan gap: Eighty-five percent of Democrats approve of his job performance while just 9 percent of Republicans agree. Among independents - key swing voters in presidential elections - 47 percent approve while 50 percent disapprove, underscoring Obama's work ahead.

More than anything, the 2012 campaign remains about the economy and its impact on public perceptions. A vast 89 percent continue to rate the economy negatively; however, the number who give it the worst rating, "poor," has declined to 42 percent, from 50 percent in July. It matters: Among registered voters who say the economy's merely not so good, Obama leads Romney by 62-35 percent. Among those who say it's poor, Romney leads, 65-29.

Largely based on these levels of economic discontent, 75 percent describe themselves as dissatisfied or even angry with the way the federal government is working - broad continued rejection of the status quo, albeit down slightly from a record 80 percent in July and November alike. That can put incumbents at serious risk.

Indeed, on a basic measure of anti-incumbency, 53 percent of Americans say they're inclined to look for someone new to support for Congress, rather than vote to re-elect their representative. While a majority, that's down sharply from a record 69 percent in August - a result that buys some breathing room for incumbents generally, and for Obama in particular.

METHODOLOGY - This ABC News/Washington Post poll was conducted by telephone Feb. 1-4, 2012, among a random national sample of 1,000 adults, including landline and cell-phone-only respondents. Results have a margin of sampling error of 4.0 points for the full sample. The survey was produced for ABC News by Langer Research Associates of New York, N.Y., with sampling, data collection and tabulation by Abt-SRBI of New York, N.Y.