WASHINGTON (Reuters) - Democrat Barack Obama and Republican John McCain faced the verdict of U.S. voters on Tuesday after a long and bitter struggle for the White House, with Obama holding a decisive edge in national opinion polls.

At least 130 million Americans were expected to vote on a successor to unpopular Republican President George W. Bush and set the country's course for the next four years to tackle the economic crisis, wars in Iraq and Afghanistan, an overhaul of health care and other issues.

Long lines of voters waited their turns at many locations. Polls close in parts of Indiana and Kentucky at 6 p.m. EST and over the following six hours in the other 48 states and the District of Columbia.

Obama, 47, a first-term senator from Illinois, would be the first black U.S. president. Opinion polls indicate he is running ahead of McCain in enough states to give him more than the 270 electoral votes he needs to win.

A victory for McCain, 72, would make him the oldest president to begin a first term in the White House and make his running mate Sarah Palin the first female U.S. vice president.

World stocks rose to a two-week high as investors focused on the election, and U.S. stocks opened higher on Wall Street with major indices up more than 2 percent.

Analysts have said market prices probably already reflected expectations of an Obama victory. But if Democrats tighten their control of Congress, it may be easier for the new administration to deal with the financial crisis.

Nearly 31 million voters were estimated to have cast ballots before Election Day, taking advantage of early-voting options that have spread to 34 of the 50 U.S. states. But long lines of people waited to vote at some polls in battleground states including Pennsylvania, Ohio and Virginia.

Ian Edwards, 60, said he voted for Obama.

"Very simple," the chief executive of a small technology company said in explaining his vote at a Cincinnati polling place. "Bad war. Bad economy. Bad reputation overseas."

McCain voter Tyler White, in Scottsdale, Arizona, cited the Republican's Iraq war policy and said he distrusted Obama on taxes. "My parents are in the upper tier of the tax bracket and feel that Barack Obama is not the right fit," he said.

JOURNEY ENDS

Obama and his wife, Michelle, avoided the line at his Chicago polling station as they were let in a side entrance with their two daughters to vote. Poll workers and voters snapped pictures and cheered.

"When polls close, the journey ends but voting with my daughters, that was a big deal," Obama said afterward, on his way to Indiana for one last campaign appearance.

McCain also planned Election Day rallies. "We're going to work hard until the polls close," McCain, an Arizona senator, told CBS news.

McCain embraced his role as an underdog and said he was gaining on Obama. He finished a cross-country, seven-state tour in his home state of Arizona early Tuesday as he sought the biggest upset in modern politics.

Obama won in Dixville Notch, New Hampshire, the tiny hamlet that traditionally holds presidential voting right after midnight. He gained 15 votes to McCain's six, becoming the first Democrat to win there since Hubert Humphrey in 1968.

Both candidates hammered their campaign themes in the race's final hours, with Obama accusing McCain of representing a third term for Bush's policies and being dangerously out of touch on the economy.

McCain, whose campaign has attacked Obama as a socialist and accused him of being a "pal" with terrorists, portrayed him as a liberal who would raise taxes.

OBAMA LEADING IN RED STATES

Opinion polls showed Obama ahead or even with McCain in at least eight states won by Bush in 2004, including the big prizes of Ohio and Florida. Obama led comfortably in all of the states won by Democrat John Kerry in 2004.

McCain has struggled to separate himself from Bush in a difficult political environment for Republicans, who are trying to hold on to the presidency for a third consecutive term.

Victories in any of the traditionally Republican states where polls show Obama is competitive, including Virginia, Colorado, Indiana and North Carolina, would likely propel him to the White House.

He took command of the race in the last month as a deepening financial crisis reinforced his perceived strengths on the economy, and in three debates.

Democrats are also expected to expand majorities in both chambers of Congress. They need to gain nine Senate seats to reach a 60-seat majority that would give them the muscle to defeat Republican procedural hurdles.

That would increase pressure on Democrats to deliver on campaign promises to end the war in Iraq, eliminate Bush's tax cuts for the wealthy and overhaul a health care system that leaves 47 million Americans uninsured.

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