WASHINGTON (Reuters) - Democrat Barack Obama has opened an 8-point national lead on Republican John McCain as the U.S. presidential rivals turn their focus to a general election race, according to a Reuters/Zogby poll released on Wednesday.

A combination photo of Democratic presidential candidate Senator Barack Obama (L) and Republican presidential candidate Senator John McCain. REUTERS/John Gress (L) and Amir Cohen

Obama, who was tied with McCain in a hypothetical head-to-head matchup last month, moved to a 48 percent to 40 percent lead over the Arizona senator in May as he took command of his grueling Democratic presidential duel with rival Hillary Clinton.

The Illinois senator has not yet secured the Democratic presidential nomination to run against McCain in November.

The poll also found Obama expanded his lead over Clinton in the Democratic race to 26 percentage points, doubling his advantage from mid-April as Democrats begin to coalesce around Obama and prepare for the general election battle with McCain.

“Obama has been very resilient, bouncing back from rough periods and doing very well with independent voters,” pollster John Zogby said. “The race with McCain is going to be very competitive.”

The poll was taken Thursday through Sunday during a period when Obama came under attack from President George W. Bush and McCain for his promise to talk to hostile foreign leaders without preconditions.

Obama’s gains followed a month in which he was plagued with a series of campaign controversies and suffered two big losses to Clinton in Pennsylvania and West Virginia.

The poll was conducted after Obama denounced his former pastor, the Rev. Jeremiah Wright, who made a series of public appearances that rekindled a controversy over his inflammatory comments on race and religion.

Obama also survived a furor over his comments about “bitter” small-town residents who cling to guns and religion out of frustration over their economic concerns.

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Obama edged closer to clinching the Democratic nomination on Tuesday when he split two nominating contests with Clinton, beating the New York senator in Oregon and losing in Kentucky to gain a majority of pledged delegates won in state-by-state nominating contests.

The results put him within easy range of the 2,026 delegates needed for the nomination. Just three Democratic nominating contests remain before voting concludes on June 3.

OBAMA BETTER ON ECONOMY

The poll found Obama was seen as a better steward of the economy than McCain, leading 48 percent to 39 percent. McCain led Obama by 3 points last month on an issue that is certain to be crucial in their campaign.

Obama led McCain among independents, 47 percent to 35 percent, and led among some groups of voters who have backed Clinton during their Democratic primary battle, including Catholics, Jews, union households and voters making less than $35,000 a year.

McCain led among whites, NASCAR fans, and elderly voters. McCain led with voters who believed the United States was on the right track, and Obama led with the much higher percentage of voters who believed it was on the wrong track.

“Clearly voters are looking for change. Every problem Obama has had in consolidating his base and reaching to the center, John McCain has the same sort of problem,” Zogby said.

“It’s McCain’s lead among voters over the age of 65 that is keeping him within shouting distance of Obama,” he said.

The poll found Clinton, who has shrugged off calls to quit the Democratic race, tied at 43 percent with McCain in the national poll. She led McCain by 47 percent to 40 percent on who would be the better manager of the economy.

Obama and Clinton have refrained from attacking each other in recent weeks as Obama has turned his focus to McCain.

But Zogby said the attacks on Obama by Bush and McCain, who have been critical of his willingness to talk to leaders of countries like Iran, did not appear to hurt Obama. If anything, he said, it reminded voters of McCain’s ties to Bush, whose approval rating is still mired at record lows.

“The president is so unpopular. To inject himself into a presidential campaign does not help John McCain, particularly when McCain is tied to Bush,” Zogby said.

The national survey of 516 likely Democratic primary voters had a margin of error of 4.4 percentage points. The poll of the national race between McCain and the two Democratic contenders surveyed 1,076 likely voters with a margin of error of 3 percentage points.

(Editing by Doina Chiacu)