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 now leads in all of the states won by Democrat John Kerry in 2004 and in two -- Iowa and New Mexico -- won by Republican President George W. Bush, recent polls show.

If Obama wins those states in the November 4 election he would have 264 electoral votes, within striking distance of the 270 electoral votes needed to win the Electoral College and capture the White House.

The U.S. 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, putting it near the top of Obama's target list. A weekend poll had Obama and McCain tied at 44 per cent, although earlier polls put Obama ahead by as much as 9 points as McCain's post-convention momentum faded and the financial crisis took 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's diverse population makes it a classic swing state with a heavy concentration of older voters who could favor McCain and Jewish voters who are normally Democratic but have been wary of Obama. Four new polls last week gave Obama, who had trailed in Florida for weeks, a slight edge in a state McCain must win.

* Michigan -- 17 electoral votes. Kerry won by 3 percentage points in 2004, and the Michigan'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 out to a significant edge in recent surveys and McCain announced on Thursday that he is pulling out of the state.

* New Hampshire -- Four electoral votes. Kerry beat Bush here 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 recent polls give Obama a double-digit lead.

* 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. Two recent polls put Obama ahead by between five and eight 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. Three new polls this week showed the race close -- one gave a slight edge to McCain and two showed a small lead for Obama.

* 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. One weekend poll had Obama ahead by seven points, although earlier polls were closer and yielded a split result.

* 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. Polls this week showed Obama moving out to a significant lead. One poll had him ahead by 15 points.

* 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. Three polls this week gave Obama a slight edge and one showed 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. A new survey on Thursday gave Obama a nine-point lead.

(Writing by John Whitesides; Editing by Andrew Quinn and Frances Kerry)