In an election year in which the economy ranks as Americans’ top concern, presumptive Republican presidential nominee Mitt Romney holds significant advantages over President Obama among white voters who are struggling financially and buffeted by job loss, according to a new Washington Post-ABC News poll.

Asked which candidate would do more to advance their families’ economic interests, middle-class white voters who say they are struggling to maintain their financial positions chose Romney over Obama by a large margin — 58 percent to 32 percent.

The former Massachusetts governor has a similar advantage on this question among white voters who have lost a job in recent years, or who have seen a family member or close friend face unemployment.

Nonwhite voters, struggling or not, give Obama huge leads over Romney when it comes to looking after their families’ financial interests.

The results underscore a continuing challenge for Obama and the Democratic Party with white voters, and particularly those without college degrees — who, according to the Bureau of Labor Statistics, are significantly more likely to be unemployed than those with higher education.

Indeed, among whites who described themselves as struggling to maintain their economic footing — regardless of their current class — nearly seven in 10 lacked a college diploma. And although they lean more Republican than the population in general, it is a group that neither party can ignore. In the new poll, 31 percent of these voters described themselves as Republicans, 27 percent as Democrats.

In 2008, Obama lost whites without college degrees by a big margin, 58 percent to 40 percent, according to the national exit poll. That performance among such voters was similar to John F. Kerry’s in 2004 and Al Gore’s in 2000.

“Democrats are very likely to lose those voters” again this year, said Mark Mellman, a Democratic pollster. “The question is by how much.”

One factor that may help the president is that, in the 14 or fewer swing states likely to determine the outcome of the election, unemployment rates have dropped more sharply than they have for the nation as a whole.

But the extended economic hardship many Americans are facing — across racial and partisan lines — makes those who are vulnerable a particularly important target group for both campaigns.

The president’s reelection team is attempting to portray Romney as out of touch with and unsympathetic to the anxieties of middle-class Americans. A much-talked-about Obama campaign advertisement airing in Ohio depicts Bain Capital, a private-equity firm that Romney founded, as a “vampire” that sucked the last financial lifeblood of failing companies at the expense of their workers.

All of the people featured in the ad criticizing Bain appear to be white.

The spot, however, has brought criticism from within the president’s party, including from Edward G. Rendell, a former Pennsylvania governor and Democratic Party chairman. They have expressed concern that the tone of the attack will make the party appear to be opposed to the private-equity industry, which is an important player in the national economy and a major source of campaign contributions.

Romney, meanwhile, portrays the president as out of his depth on economic issues. And in the Republican’s current advertising campaign, he highlights steps he would take as president to roll back policies that the Obama administration has put into place.

In the poll, Americans overall reported widespread economic pain, with more than seven in 10 saying they have been affected directly or indirectly by unemployment in the past few years. Four in 10 report struggling to maintain their socioeconomic status, with about one in five saying they are in the middle class and straining to stay there.

Fifty percent of all voters say Obama would do more to advance the interests of the middle class more generally, and 44 percent say so of Romney.

On that question, Obama has an advantage of 53 percent to 41 percent among those who think their foothold in the middle class is relatively secure, while the two candidates divide about equally among those struggling to stay there.

That overall parity, as has been the case in the past, disguises a vast racial divide.

Among white voters trying to stay in the middle class, Romney is considered the better candidate for that group by a 20-point margin; Obama is preferred by better than 3 to 1 among middle-class nonwhite voters, regardless of their sense of security.

Whites and nonwhites — as well as voters across party lines — agree that Romney would do more than Obama to advocate for the economic interests of wealthy Americans.

By a 23-point margin, voters say it’s Romney, not Obama, who would do more to advance the interests of Wall Street.

As for the new federal regulations for banks and other financial institutions put in place during the current administration, few voters — about one in four — say they have struck the right balance. About 25 percent of all voters say the regulations “go too far,” while 39 percent say “not far enough.” Most Democrats say the new rules are not sufficiently tough; among Republicans, twice as many say they are unnecessarily restrictive compared with those saying they are too lenient. Independents tilt in the “not far enough” direction.

The telephone poll was conducted May 17 to 20 among a random national sample of 1,004 adults. The margin of sampling error for the full poll is plus or minus 3.5 percentage points. The margin is four points for the sample of 874 registered voters.

Polling analyst Scott Clement and polling manager Peyton M. Craighill contributed to this report.