SCENARIOS: How candidates are faring in key states

(Reuters) - The U.S. presidential election on November 4 hinges on a handful of battleground states where opinion polls show Democrat Barack Obama making significant gains against his Republican rival, U.S. Sen. John McCain of Arizona.

Obama leads in all of 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.

A candidate 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 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 details about each state contest.

* Colorado -- Nine electoral votes. Bush beat Kerry 52 percent to 47 percent in the state in 2004 but since then Democrats have won the state legislature and governor's office. One weekend poll showed Obama ahead by 10 points, holding a lead that opened as the financial crisis moved to center stage in the campaign.

* Florida -- 27 electoral votes. Bush beat Kerry 52 percent to 47 percent in a state known for the disputed result that decided the 2000 election. Florida is a swing state with a heavy concentration of older voters who could favor McCain. It also has many Jewish voters who are normally Democratic but have been wary of Obama. A poll on Saturday gave Obama a 5-point edge, the latest in a string of surveys that have shown him leading in a state that McCain must win to take the presidency.

* Indiana -- 11 electoral votes. Bush beat Kerry by 20 points in 2004 in a state that last voted for a Democrat in 1964. But it borders Obama's native Illinois and he has poured resources into his Indiana campaign after finishing a strong second to Sen. Hillary Clinton in the May Democratic primary. Republicans have begun to advertise there but polls have shown Obama closing the gap. The two most recent polls gave McCain a lead of between 5 and 7 points.

* Michigan -- 17 electoral votes. Kerry won by 3 points in 2004. The state's depressed economy and ailing manufacturing base make it a prime target for competing arguments by the candidates on the economy. One poll after the Republican convention last month showed the race dead even but Obama has opened a significant edge in recent surveys and McCain pulled his campaign from Michigan on October 2.

* Missouri -- 11 electoral votes. Bush beat Kerry 53 percent to 46 percent in 2004 in a battleground with a mix of urban centers in Kansas City and St. Louis and conservative rural areas more aligned culturally with the South. After trailing early, Obama has closed the gap on McCain in recent weeks and led by 3 points in a poll last week.

* New Hampshire -- Four electoral votes. Kerry beat Bush by 1 point in 2004. 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 of the state's seats in Congress and gained control of the state legislature in 2006 in an anti-Republican wave on which Obama hopes to capitalize. Three polls last week show Obama leading by 8 to 13 points.

* New Mexico -- Five electoral votes. Bush beat Kerry by fewer than 6,000 votes in 2004. As the senator from neighboring Arizona, McCain is familiar to many New Mexico voters but will have to battle Obama for the growing bloc of Hispanics, who make up more than 40 percent of the state's population. Three recent polls put Obama ahead by 5 to 8 points.

* Nevada -- Five electoral votes. Bush beat 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. A poll on Sunday gave Obama a 2-point lead.

* North Carolina -- 15 electoral votes. Bush beat Kerry by 12 points in 2004 even though the Democratic vice presidential nominee, John Edwards, was from the state. But more than a fifth of the population is black and an influx of transplants to high-tech urban areas like Charlotte and the Research Triangle of Raleigh, Durham and Chapel Hill has given Obama a chance. He has visited the state several times and the most recent polls show North Carolina essentially even although one survey on Saturday had McCain ahead by 2 points.

* Ohio -- 20 electoral votes. 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 McCain will have a hard time piecing together a win without the state. The race continues to look tight, with one weekend poll showing McCain up by 2 points. Four others last week gave Obama leads of 2 to 6 points.