FACTBOX: Key states in presidential race

(Reuters) - The U.S. presidential race between Republican John McCain and Democrat Barack Obama ultimately will be decided in about 10 states where their battle remains close.

Each candidate is battling for the 270 electoral votes needed to win the White House. The president is determined not by who gets the most votes nationally but by the Electoral College, which has 538 members allotted to all 50 states and the District of Columbia in proportion to their representation in Congress.

All of the states except Maine and Nebraska award their votes to the popular vote winner in the state. Maine and Nebraska split them by congressional district.

Here are some of the key battleground states in the November 4 election, with their electoral vote totals, 2004 results and some recent details about the contests in each state.

* Colorado -- 9 electoral votes. President George W. Bush beat Democrat John Kerry 52 percent to 47 percent here in 2004, but since then Democrats have captured the state legislature and governor's office, putting it near the top of Obama's target list. Polls continue to give Obama a slight lead, even after McCain's post-convention boost in momentum.

* Florida -- 27 electoral votes. Bush beat Kerry 52 percent to 47 percent in a state infamous for the disputed result that decided the 2000 race. Florida's diverse population makes it a classic swing state, with a heavy concentration of older voters who could favor McCain and of Jewish voters who are normally Democratic but have been wary of Obama. Polls give McCain a solid lead at this stage.

* 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. Obama has narrowly led most recent polls, although one poll after the Republican convention showed the race dead even.

* New Hampshire -- 4 electoral votes. Kerry narrowly beat Bush here by one 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 Obama hopes to capitalize on. Most polls show Obama with a slight lead.

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

* Nevada -- 5 electoral votes. Bush beat Kerry by 20,000 votes in 2004 in a state won by Republicans in 8 of the last 10 presidential elections. Like New Mexico, the burgeoning Hispanic population will be crucial -- they now make up nearly a quarter of the state's residents.

* 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. Polls show a tight race.

* 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 sees a chance to reverse the result. Polls have given Obama a steady 4 to 7 point lead for months, but that narrowed after McCain's post-convention surge.

* 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 has trended toward Democrats in recent state elections amid dramatic growth in the Democratic-leaning northern suburbs of Washington D.C. McCain has a narrow lead in most recent polls.

* 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.

(Writing by John Whitesides; Editing by Patricia Wilson and David Wiessler)