SCENARIOS: How Obama, McCain are faring in key states

(Reuters) - Next week's U.S. presidential election will be decided in a handful of battleground states where opinion polls show Democrat Barack Obama mostly in the lead against Republican rival John McCain.

Obama, who leads in virtually every national opinion poll, is also 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 will need 270 electoral votes to win the Electoral College and capture the White House in Tuesday's election.

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. 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. A Wednesday poll had Obama ahead by 8 points, the latest in a string of surveys to give him similar margins.

* 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 classic swing state with many older voters who could favor McCain along with Jewish voters who are normally Democratic but have been wary of Obama. The latest poll on Wednesday gave Obama a 4-point lead, while two earlier surveys put his lead at 2 points.

* 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 home state of Illinois and he has poured resources into his Indiana campaign after finishing a strong second to Sen. Hillary Clinton in the May Democratic primary. One Wednesday poll had Obama leading by 1 point, the latest survey to describe a razor-tight race in the state.

* Missouri -- 11 electoral votes. Bush beat Kerry 53 percent to 46 percent in 2004 in a classic battleground with a mix of urban centers and conservative rural areas. McCain was up by 2 points in one Wednesday poll, while an earlier poll had shown a tied race.

* 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 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. The four most recent polls all show Obama with a significant lead, in one case by as much as 25 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 he will have to battle Obama for the growing bloc of Hispanics, who make up more than 40 percent of the state's population. A Wednesday poll gave Obama a 10-point lead, while other recent surveys have shown him ahead by between 5-8 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 Thursday showed Obama with a 7-point lead, while other polls in recent days have shown him up by as much as 12 points.

* 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. More than one-fifth of the population is black and an influx of transplants to high-tech urban areas have given Obama a chance. A Thursday poll showed a 6-point Obama lead, while earlier surveys had described the race as a tie.

* 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. A Thursday poll gave Obama a 4-point lead, while one on Wednesday had him up by 3 points -- down from wider leads earlier in the week.

* Pennsylvania -- 21 electoral votes. Kerry beat Bush 51 percent to 48 percent in 2004, but Pennsylvania is one of a handful of states won by Kerry where McCain's camp had seen a chance to reverse the result. Three of the last four polls had Obama with double-digit leads, while another described his lead as 4 points.

* Virginia -- 13 electoral votes. 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's trend has been toward Democrats in recent state elections amid dramatic growth in the Democratic-leaning northern suburbs of Washington, D.C. The most recent poll both had Obama ahead by 9 points.

* Wisconsin -- 10 electoral votes. Kerry won by 11,000 votes out of more than 3 million in 2004, but Obama has held a lead for months in a state where he crushed Hillary Clinton in a February Democratic primary showdown. A Tuesday poll gave Obama a 9-point lead.

(Compiled by Andrew Quinn in Washington; Editing by Vicki Allen)