Last week’s Democratic National Convention helped President Obama improve his standing against Republican Mitt Romney, according to a new Washington Post-ABC News poll, but did little to reduce voter concern about his handling of the economy.

The survey shows that the race remains close among likely voters, with Obama at 49 percent and Romney at 48 percent, virtually unchanged from a poll taken just before the conventions.

But among a wider sample of all registered voters, Obama holds an apparent edge, topping Romney at 50 percent to 44 percent, and has clear advantages on important issues in the campaign when compared with his rival.

The survey highlights why Obama continues to try to frame the election as a choice between himself and Romney, while Romney would like it to be a referendum on the president’s record.

The poll represents the initial public reaction to the two back-to-back conventions, and the results underscore how critical get-out-the vote efforts will be to the outcome of the contest.

With only Labor Day weekend separating the conventions in Tampa and Charlotte, and the ­barrage of television advertising and campaign activity preceding them, the events’ impact on the campaign may be less than in previous years.

Historically, candidates often get an immediate post-convention boost, with some of the shift dissipating quickly. Obama has a six-point edge among all voters based on interviews Friday, the day after the Democratic convention wrapped up. In interviews Saturday and Sunday, the two were about evenly matched among registered voters.

Obama’s relative strength emerges when all voters are asked to compare the two contenders on a series of issues and attributes. On 15 items, Obama has significant leads on eight, Romney on zero. Romney also no longer has the pre-convention advantages he held on dealing with the economy and what had been his best issue, handling the federal deficit.

The president holds double-digit leads in areas of particular focus at his party’s convention, including addressing women’s issues (Obama leads Romney by 21 percentage points), advancing the interests of the middle class (15 points), and social issues such as abortion and same-sex marriage (11 points). Obama also has a fresh, albeit slender, lead on dealing with taxes.

Three new questions emphasize the president’s advantage over Romney when it comes to personal attributes. By a margin of nearly 20 points, voters are more apt to say they would like to have Obama as a dinner guest, and the president also leads by double digits as the person voters would want to take care of them if they were sick and who they say would make a more loyal friend.

But the poll also shows how hard it is to translate any of these advantages on attributes into electoral gains. Despite a feverish effort at the Democratic convention, neither Obama nor his prominent supporters were able to reverse disapproval of the president’s handling of the economy, the dominant issue in the campaign, or inspire confidence that things will pick up if he is reelected.

Compared with the survey taken before the convention, voters’ assessments of Obama’s job performance are essentially unchanged — and in vulnerable territory — with 48 percent approving and 50 percent disapproving. Also stubbornly unchanged is the negativity around his handling of the economy: Most voters — 53 percent — disapprove of his stewardship of the economy, and strongly negative views are almost twice as common as strongly positive ones.

For more than two years, a majority of voters have disapproved of Obama in this area. Those who disapprove overwhelmingly say it is because they think he is pursuing the wrong policies, not because his efforts need more time.

A plurality of voters, 43 percent, say the nation’s economy has gotten worse since Obama took office, while fewer, 32 percent, say it has improved. The rest say it has stayed about the same. Those who see no improvement largely blame the president, although just 38 percent say they think things would be better now had Romney become president in 2009.

The rhetorically powerful “Are you better off now than you were four years ago?” question was a centerpiece of the Republican convention, and in the poll, more voters say they are worse off, rather than better, under Obama. But unlike those who see no progress for the national economy, those who view themselves as no better off since Obama became president are divided on whether they blame him for the lack of improvement.

Overall, voters split evenly between Romney and Obama when it comes to supporting small businesses, but Romney has exploitable advantages here. He has said repeatedly that he knows more about building businesses than Obama, and voters agree. About two-thirds say Romney understands what it takes to create a successful small business, while there is a split verdict on Obama. By 53 percent to 35 percent, more say government programs do more to hamper than bolster small businesses.

Obama has hammered Romney for not explaining the details of his tax and budget proposals, and 61 percent of voters say the Republican has not done enough to lay out the policies he would enact. But for the incumbent, things are hardly positive here: Six in 10 Americans agree that Romney has not done enough to provide those details. But 49 percent also say Obama hasn’t done enough to specify a second-term agenda.

The new poll shows an electorate more tuned into the campaign than it was two weeks ago, with enthusiasm and the solidity of voters’ preferences reaching new highs for the cycle. More than six in 10 voters say they need no more information to make a choice, indicating a hardening of the battle lines, as well as the dwindling number of truly undecided or “movable” voters.

More than nine in 10 Obama supporters say they are enthusiastic, with 56 percent saying they are “very enthusiastic.” Almost nine in 10 Romney backers say they are enthusiastic, with 46 percent saying they are strongly backing him.

Although Obama outpaces Romney when it comes to enthusiastic backers, he has fewer such supporters now than he did at this time four years ago. And younger people are notably less enthusiastic and less certain they will vote than they were in 2008.

The telephone poll was conducted Sept. 7 to 9 among a random national sample of 1,002 adults, including 826 registered voters. The margin of sampling error among the sample of registered voters is plus or minus four percentage points.

Peyton M. Craighill, Scott Clement and Jenna Fulton contributed to this report.