Democrat Barack Obama and Republican John McCain faced the verdict of US voters yesterday 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 cast votes on a successor to 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 healthcare and other issues.

Poll stations were open across more than half the United States at midnight Beijing time and TV stations showed long lines of voters in many places. They will close in parts of Indiana and Kentucky at 7 am Beijing time and over the following six hours in the other 48 states and the District of Columbia.

Opinion polls indicate Obama is running ahead of McCain in enough states to give him more than the 270 electoral votes he needs to win.

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 US states. But long lines of people waited to vote at some polls in battleground states including Pennsylvania, Ohio and Virginia.

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.

Both candidates planned to campaign on election day. "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 yesterday as he sought the biggest upset in modern politics.

In Prescott, McCain spoke of the state's record of bad luck in getting Arizona candidates elected to the White House. "We're going to reverse that unhappy tradition and I'm going to be the president of the United States," he told the crowd.

Obama won in Dixville Notch, New Hampshire, the tiny hamlet that traditionally opens 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.

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.

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.

Turnout could decide the outcome, and both campaigns revved up multi-million-dollar operations to get voters to the polls.

Questions:

1. How many voters are expected to cast ballots on Election Day?

2. What are the main issues Americans are concerned about?

3. Which states would Barack Obama need to win to get into the White House?

Answers:

1. 130 million.

2. The economic crisis, wars in Iraq and Afghanistan, and healthcare.

3. Virginia, Colorado, Indiana and North Carolina.