WASHINGTON - TUESDAY'S US presidential election will be decided in about a dozen battleground states where most opinion polls show Democrat Barack Obama ahead of Republican rival John McCain.

Mr Obama, who leads in every national opinion poll, is ahead in all the states won by Democrat John Kerry in 2004 as well as in several states won by Republican President George W. Bush, recent polls show.

The victor needs 270 electoral votes to win the Electoral College and capture the White House.

The president is determined not by the most votes nationally but by a majority of the Electoral College, which has 538 members allotted to all 50 states and the District of Columbia in proportion to their representation in Congress.

Each state, except Maine and Nebraska, awards its votes to the candidate who gets the most votes in the state. Maine and Nebraska split them by congressional district.

Here are some battleground states with their electoral vote totals, 2004 results and recent details about the contests in each state.

* Colorado - Nine electoral votes. Mr Bush beat Mr Kerry 52 per cent to 47 per cent in the state in 2004, but since then, Democrats have won the state legislature and governor's office.

The two latest polls put Mr Obama up by 7 and 5 points respectively.

* Florida - 27 electoral votes. Mr Bush beat Mr Kerry 52 per cent to 47 per cent in a state known for the disputed result that decided the 2000 election. Florida is a classic swing state with many older voters who could favour Mr McCain along with Jewish voters who are normally Democratic but have been wary of Mr Obama.

The most recent polls give Mr Obama a lead of between 2 points and 7 points.

* Indiana - 11 electoral votes. Bush beat Mr Kerry by 20 points in 2004 in a state that last voted for a Democrat in 1964. But it borders Mr Obama's home state of Illinois and he has poured resources into his Indiana campaign after finishing a strong second to Senator Hillary Clinton in the May Democratic primary. The race remains a toss up, with the two most recent polls showing the state a dead heat.

* Missouri - 11 electoral votes. Mr Bush beat MrKerry 53 per cent to 46 per cent in 2004 in a classic battleground with a mix of cities and conservative rural areas. In the two most recent polls, the race was dead even or MrMcCain was ahead by one point.

* New Hampshire - Four electoral votes. MrKerry beat MrBush by 1 point in 2004. Mr McCain's history of big primary wins in New Hampshire in 2000 and this year gives him hope he can take the state in November. Democrats captured both the state's seats in Congress and gained control of the state Legislature in 2006 in an anti-Republican wave on which Mr Obama hopes to capitalise. All 5 of the most recent polls show Mr Obama ahead with a lead ranging from 7 to 15 points.

* New Mexico - Five electoral votes. Mr Bush beat Kerry by fewer than 6,000 votes in 2004. As the senator from neighboring Arizona, Mr McCain is familiar to many New Mexico voters, but he will have to battle Mr Obama for the growing bloc of Hispanics, who make up more than 40 per cent of the state's population. The most recent poll shows Mr Obama ahead by 10 points.

* Nevada - Five electoral votes. Mr Bush beat Mr Kerry by 20,000 votes in 2004 in a state won by Republicans in eight of the past 10 presidential elections. As in New Mexico, the burgeoning Hispanic population will be crucial - it now makes up nearly a quarter of Nevada's residents. Two recent polls gave Mr Obama a 4-point lead, and another had his advantage at 5 points.

* North Carolina - 15 electoral votes. Mr Bush beat Mr Kerry by 12 points in 2004, even though the Democratic vice presidential nominee, Mr John Edwards, was from the state.

More than one-fifth of the population is black and an influx of transplants to high-tech urban areas have given Obama a chance. One recent poll showed the race even, another gave Mr McCain a 3-point edge and another gave Mr Obama a 2-point edge.

* Ohio - 20 electoral votes. Mr Bush beat Kerry by about 120,000 votes in the state that ultimately decided the 2004 race. No Republican has won the White House without Ohio, and Mr McCain will have a hard time piecing together a win without the state. One new poll gave Mr McCain a 2-point lead, while others have given Mr Obama a 4-point to 6-point edge.

* Pennsylvania - 21 electoral votes. Mr Kerry beat Mr Bush 51 per cent to 48 per cent in 2004, but Pennsylvania is one of a handful of states won by Mr Kerry where Mr McCain's camp had seen a chance to reverse the result. The most recent polls give Mr Obama a 4-point to 6-point edge.

* Virginia - 13 electoral votes. Mr Bush won fairly easily by 9 points in 2004 in a state that has not gone Democratic in a presidential election since 1964. But Virginia has trended toward Democrats in recent state elections amid dramatic growth in the Democratic-leaning northern suburbs of Washington, D.C.

Four polls in the last four days have given Mr Obama a lead of between 3 points and 9 points.

* Wisconsin - 10 electoral votes. Mr Kerry won by 11,000 votes out of more than 3 million in 2004, but Mr Obama has held a lead for months in a state where he crushed Mrs Hillary Clinton in a February Democratic primary showdown. The three most recent polls show Mr Obama ahead by 10, 11 and 16 points, respectively. -- REUTERS