President Bush holds clear advantages over John F. Kerry on national security issues and leadership in the war on terrorism, largely erasing the broad gains Kerry made at his party's Boston convention last month, but voters continue to give the president negative marks on the economy and his handling of Iraq, according to a new Washington Post-ABC News poll.

At the opening of the Republican National Convention, Bush and Kerry remained deadlocked in the race for the White House, with each claiming 48 percent of likely voters, with 1 percent supporting independent Ralph Nader, virtually unchanged from a survey taken immediately after the Democratic convention. Among all registered voters, the poll found Bush at 48 percent and Kerry at 47 percent, a shift in the president's direction since the previous survey.

The survey offered conflicting evidence of the impact of the controversy over Kerry's Vietnam War record and television ads attacking his character aired by a group called Swift Boat Veterans for Truth. A solid majority of voters said they believe that Kerry deserved the medals he won in Vietnam, and most voters characterized the issue of Vietnam as irrelevant to their choice in November. But in the past month, Kerry's personal image has deteriorated, with almost as many voters viewing him unfavorably as favorably.

The new poll confirms the suggestion by other recent surveys that, despite clear dissatisfaction about the direction of the country, Bush has regained ground lost to Kerry on national security issues. Republicans will now attempt to build on those shifts during their four-day convention, which opened yesterday in New York. Bush advisers see the convention as an opportunity to highlight the president's leadership in the war on terrorism and also to attack Kerry's Senate record in an effort to portray him as inconsistent and unreliable.

The new poll found that a slight majority of registered voters -- 53 percent -- say Bush is more qualified than Kerry to be commander in chief, while 43 percent say they prefer the Democratic nominee. At the end of the Democratic convention, Kerry enjoyed an eight-point advantage over Bush on that question. Taken together, the results of the poll suggest that Bush's recent gains have come from eroding perceptions of Kerry and not as a consequence of improved views of Bush's performance as president.

"I like the way [Bush] has handled [Iraq] -- he just did what he had to do, didn't pussyfoot around," said Joy L. Crockett, 52, a manicurist in Hammond, La. She said she worries that Iraq and the war on terrorism make it a bad time to change presidents and believes that Bush offers the best hope to "get the country back to better than it was."

But others worried that Bush's go-it-alone leadership style has isolated the United States from the rest of the world at precisely the time that the country needs help from its allies to stabilize Iraq and fight the international war on terrorism.

"He's alienated the U.N. -- if anyone in government thinks they're going to get any countries like France to pay for some of this, I want some of what they're smoking. They'll be laughing up their sleeves," said William Thomas, 66, a retired electrician who lives in a suburb of Cleveland.

A total of 1,207 randomly selected adults was interviewed Aug. 26-29, including 945 registered voters and 775 likely voters. The margin of sampling error for the subsample of likely voters is plus or minus three percentage points; it is slightly smaller for all voters.

Bush's job approval rating stands at 50 percent, where it has largely been for the past six months. Fewer than half of all voters -- 45 percent -- approve of the job Bush is doing on the economy, unchanged from recent Post-ABC News polls. Fewer than half also approve of the way he is dealing with the situation in Iraq, also unchanged.

On other issues such as education and health care, public sentiments remain unchanged from a month or two ago. Six in 10 voters give Bush high marks for the way he has handled the war on terrorism, up slightly from last month but still below where it was as recently as April.

Overall, a majority of voters -- 54 percent -- said they are dissatisfied with the way things are going in the country, unchanged from July and a sign that Bush remains vulnerable despite his recent gains.

"It's sort of like we're stuck -- Iraq is a quagmire-type deal. Myself, I'm concerned with keeping a job; I work two jobs," said Karen Barnes, 50, of Indianapolis. "Trade is a big issue -- I know we have to have free trade, but jobs are going overseas."

But when matched against Kerry on issues and character, Bush has either closed the gap or surged ahead on virtually every measure.

One reason is that candidates often lose some of the bounce in support they gained from their convention. But the erosion in Kerry's standing also may be attributable to the attacks on his Vietnam service and continued criticism from Bush and his campaign of the Democrat's record and reliability.

Bush is viewed as more honest and trustworthy than Kerry by 47 percent to 41 percent -- exactly reversing the results of the Post-ABC News poll taken immediately after the Democratic convention.

Bush also is seen by a growing majority as the stronger leader and has narrowed Kerry's lead from 14 percentage points to six points as the candidate who best understands the problems of people like them. He has tied Kerry as the candidate who best shares their values and drawn nearly even with the Democrat as the candidate who has a vision for the future, two areas where Kerry led immediately after his party's convention.

On key issues as well as character, Bush has improved his position since the Democratic convention. Kerry is no longer viewed as the candidate best able to deal with the economy -- an issue of growing importance to Americans this year, according to the survey. Voters are now evenly divided over which candidate would do the better job with economic issues.

By 52 percent to 44 percent, voters now judge Bush superior to Kerry as the candidate who would be best able to deal with the situation in Iraq. After the Democratic convention, the two were essentially tied.

In barely a month, Bush has surged to an 18-point advantage over Kerry as the candidate voters prefer to lead the war on terrorism. Immediately after the Democratic convention, Bush held a three-point lead over Kerry on this key measure.

The Post-ABC News survey also found that Vietnam haunts both Kerry and Bush. In recent weeks, Swift Boat Veterans for Truth has said Kerry did not deserve the medals he won for service during Vietnam and may have exaggerated other details of his service during the war.

By nearly 3 to 1, voters reject those claims and say Kerry does deserve his Vietnam medals. And two-thirds disapprove of the commercials critical of Kerry, though voters remain divided over whether the Bush campaign was behind the ads.

More broadly, most voters dismissed the issue of each candidate's military service during the Vietnam era. Six in 10 said Kerry's war record does not affect their decision to vote for him, while seven in 10 said Bush's service in the Texas Air National Guard during Vietnam is not an issue. In addition, half say Kerry's opposition to the Vietnam War after he left the military was not relevant to them, though one in four said it made them less likely to vote for Kerry, while a slightly smaller proportion said his actions made them more inclined to support him.

"It's all a sideshow," said Melissa Mathias, 24, a first-grade teacher who lives in Chrisman, Ill. "There are lot more important issues. They just pick at each other's faults -- like first-graders."