SCENARIOS: How candidates are faring in key states

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

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.

Even Florida and Ohio, pivotal states which swung the 2000 and 2004 elections to the Republicans, also appear to be leaning toward the Democratic candidate, according to poll results.

Obama or McCain need 270 electoral votes to win the Electoral College and capture the White House in the November 4 election.

The president is determined not by who gets the most votes nationally, but by who wins 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 Democrat John Kerry 52 percent to 47 percent in the state in 2004, but since then Democrats have won the state legislature and governor's office. Two polls this week show Obama ahead by 6 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 classic 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 Tuesday gave Obama a 2-point edge, the latest survey to show him with a narrow lead in a state McCain must win.

* Indiana -- 11 electoral votes. Bush beat Kerry by 20 points in 2004 in a state that last voted for a Democrat in 1964. But Indiana borders Obama's native Illinois and he has poured resources into his campaign there 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 most recent poll gave McCain a 5-point lead.

* Michigan -- 17 electoral votes. Kerry won by 3 percentage points in 2004, and 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 moved up to a significant edge in recent surveys and McCain announced last week that he is pulling his campaign out of 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 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 this week.

* New Hampshire -- Four electoral votes. Kerry beat Bush by 1 percentage point in 2004, and McCain's history of big primary wins in the state in 2000 and this year gives him hope he can push it into his column in November. Democrats captured both seats in Congress and gained control of the state legislature in 2006 in an anti-Republican wave on which Obama hopes to capitalize. Two polls this week give Obama a lead of 8 and 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 state's growing bloc of Hispanics, who make up more than 40 percent of New Mexico's population. Three recent polls put Obama ahead by between 5 and 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 the state's residents. The three most recent polls this week gave Obama a slight edge.

* 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 in 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 the state essentially even.

* 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 poll this week showing McCain up by one point and three others giving Obama leads of between 3 and 6 points.

* 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. Four polls this week have given Obama a double-digit lead.

* Virginia -- 13 electoral votes. Bush won fairly easily by 9 percentage points in 2004 in a state that hasn't 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. Two polls on Monday put Obama ahead with double-digit leads, although another gave him just a 2-point advantage. Earlier surveys were much closer and one had shown McCain leading narrowly.

* 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. Surveys this week have shown Obama up by between 5 and 10 points.

(Writing by John Whitesides; Editing by Andrew Quinn and David Wiessler)