On the eve of their second debate, President Obama and challenger Mitt Romney remain locked in a virtual dead heat nationally, with Republicans showing increased enthusiasm for their nominee after his big win in the first debate, according to a new Washington Post-ABC News poll.

Likely voters in the new poll split 49 percent for Obama to 46 percent for Romney, basically unmoved from the poll two weeks ago, just before the two candidates met in Denver for their first debate. On topic after topic, the survey portrays an electorate that remains deeply divided along partisan lines and locked in its views.

Nearly two-thirds say they do not need any more information before Election Day, and barely one in eight is undecided or says there is a chance he could change his vote. Even as voters overwhelmingly perceive that Romney won the first debate, the vast majority say their opinion of the president did not shift as a result.

But more people changed their views of Romney, largely in a positive direction. Overall, more than twice as many say their opinions of the former Massachusetts governor improved than say they worsened as a result of the debate. The strongest reaction is among Romney backers, 70 percent of whom say Denver made them think more highly of the GOP nominee.

The improvement in views of Romney carries directly into the underpinnings of his support: Fewer of his supporters now express anxiety about a Romney administration, and the number of his backers saying they support him “very enthusiastically” jumped by double digits. Among the likely voters supporting Romney, 62 percent now do so intensely, exactly double the number who were eagerly lined up behind Republican nominee John McCain at this stage in the campaign four years ago.

Presidential debate does little to change a locked in electorate

Meanwhile, enthusiasm for the president has also ticked higher, but it remains below where it was four years ago. Of course, at this time in October 2008, Obama held a 10-percentage-point lead over the Republican senator from Arizona. In the new poll, a three-point edge does not represent a statistically significant advantage.

Beyond enthusiasm, Obama lags behind 2008 in assembling a winning coalition because groups of voters highly likely to back his candidacy — including Democrats, non-whites and younger voters — are far less interested in the campaign this time around.

But the president is buoyed in the final stretch by improving attitudes about the direction of the country, although his fellow Democrats are the ones becoming more sanguine. Among all voters, 42 percent now say the country is headed in the right direction, yet another tick upward, and 13 percentage points higher than before the party conventions. Still, most — 56 percent — see things as pretty seriously on the wrong track.

Obama gets some credit — but little from Republicans — for one recent sign of improvement in the economy: the drop in the unemployment rate to 7.8 percent in September, breaking a record 43-month stretch above 8 percent. A slim majority of voters give him at least some credit for the decline, but less than one in four says he should get “a lot” of credit for it. Most Republicans, however, give him no credit at all for this, reflecting the big partisan divide on all matters.

The slip in the unemployment rate had no meaningful effect on voters’ views of Obama’s stewardship of the economy: 47 percent of all voters continue to approve of the job he is doing on the issue, and 51 percent disapprove. Majorities have consistently given the president negative reviews on the economy, going back more than two years.

A challenge for Obama and Romney is that voters remain unconvinced that either candidate, if elected, will be able to quickly turn around the economy. Head-to-head on the matter, 48 percent of all voters say they trust Obama to deal with the economy, and 44 percent side with Romney. Among likely voters, it’s an even narrower divide: 48 to 47 percent.

Voters’ preferences on the economy are little changed from two surveys last month, and there has been only isolated movement across other issues tested in the new poll. Obama continues to hold the edge when it comes to being in touch with the economic problems people are having in the country and when it comes to being seen as the more friendly and likable of the two candidates.

As before, Romney does not have statistically significant advantages in any of the tested areas — including taxes, international affairs and Medicare. But his eight-percentage-point edge among likely voters when it comes to dealing with the federal budget deficit comes close. (This question was asked of a half-sample of all respondents, with a higher margin of sampling error.)

Nor has anything shifted since the debate in perceptions about whether, as president, Romney would favor the wealthy or the middle class: 58 percent of all voters say his policies would probably favor the wealthy. Most say Obama’s policies favor the middle class, not the wealthy.

The long string of marginal shifts over previous surveys illuminates the high degree of lock-in that characterizes the campaign. After all, 48 percent of likely voters are either definitely supporting Obama or unlikely to change their minds, and 44 percent are as committed to voting for Romney.

The parity — neither Obama nor Romney has had a significant lead in any of the five times The Post and ABC have asked about likely voting — underscores the importance of voter turnout, which party will be more successful at getting out the vote. The closeness of the contest has also persisted even as the partisan makeup of the random polling samples has varied.

Partisan identification fluctuates from poll to poll as basic orientations shift and with the sampling variability that accompanies each randomly selected sample of voters. In the current poll, Democrats outnumber Republicans by nine percentage points among likely voters; the previous three Post-ABC polls had three-, six- and five-percentage-point edges for Democrats. The presidential contest would now be neck and neck nationally with any of these margins.

Overall, 25 percent of all voters say they have been personally contacted by the Obama campaign; 21 percent say this of the Romney campaign. Obama’s side may have the edge in swing states, at least in terms of contacts. About 37 percent of voters in the eight key states — the seven Post “tossup” states plus Ohio — say they’ve heard from an Obama campaign representative in the past month; 27 percent in those states say they have been contacted by one of Romney’s.

State polling across the critical states where both campaigns are focusing their efforts has not changed dramatically since the debate, with Romney picking up mainly a percentage point or so. Those small shifts — statistically insignificant but potentially substantively significant — are also reflected in this new national poll, with the contest tightening on the margin among likely voters across these eight states. The telephone poll was conducted Oct. 10-13 among a random national sample of 1,252 adults. Results for the full sample of 1,063 registered voters are plus or minus 3.5 percentage points; they are also 3.5 points for the 923 likely voters.

Scott Clement and Peyton M. Craighill contributed to this report.