HEMPSTEAD, New York (CNN) -- If the presidential election were held today, the latest update of the CNN Electoral College Map estimates Democratic candidate Barack Obama would win enough electoral votes to capture the White House.

CNN's new Electoral College Map was released Wednesday.

The new map indicates that Sen. Obama would have 277 electoral votes, with Sen. John McCain, the Republican candidate, amassing 174 electoral votes; 87 electoral votes are still up for grabs in several states.

In order to win the presidency, a candidate needs 270 electoral votes.

The new estimate for Obama is a change from CNN's October 7 Electoral College Map, which indicated he would take 264 electoral votes. Interactive: CNN's new Electoral Map Calculator

Obama picked up 13 electoral votes when Virginia was moved from the category of tossup state to a state that is leaning toward him. That put him over the 270 electoral-vote threshold needed to win the White House.

"Virginia hasn't gone Democratic in 44 years," said Alan Silverleib, CNN senior political researcher. "But a number of polls -- including our own -- now show Obama up double digits there. And, as the map shows, if Obama holds that lead, it may be enough to put him into the White House."

"Conversely, McCain really can't afford to lose Virginia's 13 electoral votes. That state is a key part of the Republican electoral coalition," Silverleib added.

In a CNN poll of polls released Wednesday evening, Obama is favored to win by 50 percent; McCain by 43 percent and 8 percent of voters are undecided.

CNN also switched North Dakota from a safe McCain state to one leaning toward McCain, and New Jersey from leaning toward Obama to safe Obama. Neither of those moves affected the overall electoral vote count in the CNN estimate. Watch more on the fight for battleground states »

"This is not good news for John McCain. He's heading in the wrong direction at a time when he needs to be gaining electoral votes, not losing them. But he's been left for dead before and has come roaring back. This election is not over yet," said CNN political editor Mark Preston.

The CNN Electoral Map is based on analysis from the CNN Political Unit and takes into account a number of factors, including polling, state voting trends, ad spending patterns, candidate visits and guidance from the campaigns, parties and political strategists. The list will be updated regularly as the campaign develops over time.

Obama's advance in traditionally red states has the GOP on the defense.

The McCain-Palin ticket has spent much of the week stumping in states where Obama seems poised for an unexpectedly strong showing.

A new CNN/Time Magazine/Opinion Research Corporation survey in Virginia released Wednesday indicates that Obama holds a 10-point lead over McCain -- 53 percent to 43 percent among likely voters. Watch how Virginia is leaning toward Obama in latest poll »

"Obama is winning men and women in Virginia, and is doing well across the state east of the Blue Ridge Mountains," CNN polling director Keating Holland said.

It's a similar story in Colorado, a state that hasn't voted for a Democrat in the race for the White House in 16 years. The new poll indicates the Illinois senator holds a four-point edge over McCain, 51 percent to 47 percent. Watch more on if Colorado could go blue »

And in Georgia, a state that Bush won by 17 points over Kerry four years ago and that hasn't voted for the Democrats in a presidential contest in 16 years, the poll suggests only a six-point lead for McCain, 51 percent to 45 percent.

The poll also indicates Obama has a five-point advantage over McCain in Florida, 51 percent to 46 percent. Twenty-seven electoral votes are up for grabs in Florida. Bush took the state by five points in the last election.

In Missouri, which Bush won in the past two presidential contests, the new poll suggests it's basically a dead heat, with McCain holding a one-point advantage over Obama, 49 percent to 48 percent.

"Of course, it's important to remember that the CNN Electoral Map is a snapshot in time," Silverleib said. "We are not predicting an Obama win on Election Day. We still have 20 days to go, and that's an eternity in politics."

CNN's Ed Hornick and Rebecca Sinderbrand contributed to this report.

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