[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/images/10/22/art.bloomberg.gi.jpg caption="Bloomberg appears headed for victory."](CNN) - A new survey suggests that New York City Mayor Michael Bloomberg, running for a third term in office, holds a 12-point lead over his Democratic rival with just one day to go before voters there head to the polls.
According to a Quinnipiac University survey released Monday morning, 50 percent of likely New York City voters support Bloomberg, running as an independent, with 38 percent backing the Democratic candidate, New York City Comptroller William Thompson. Ten percent of those questioned are undecided and 1 percent supports Stephen Christopher, the Conservative party candidate.
Bloomberg's 12 point lead is down from an 18 point advantage he held over Thompson in a Quinnipiac poll released a week ago. Bloomberg was up 15 points over Thompson in a Marist College survey that came out Friday.
The survey indicates that Bloomberg is leading overwhelmingly among Republicans, has a 40 point advantage among independent voters, while Thompson leads by 5 points among Democrats. The poll suggests a racial divide, with Bloomberg leading among white voters by 42 points and Thompson holding a 39 point advantage among African-Americans. Hispanic voters back Bloomberg by eight points.
According to the poll, only 13 percent of Thompson or Bloomberg backers say they might change their mind.
"Mayor Michael Bloomberg hangs on to his doubledigit lead the day before the election," says Maurice Carroll, director of the Quinnipiac University Polling Institute.
Bloomberg holds a much larger lead over his rival in another key campaign measure: he's spend more than $33 million on TV ads, according to an analysis of New York City's mayoral race by TNSMI-CMAG, CNN's consultant on campaign ad spending. Bloomberg's launched 50 different ads during his re-election bid, which have aired more than 11,000 times. Bill Thompson, Bloomberg's Democratic rival, has spent just over $2.66 million on TV ads.
The Republican-turned-independent mayor has outspent most of the Republicans who ran in last year's presidential primaries, according to TNSMI-CMAG's Evan Tracey - his $33 million outlay is more than three times what John McCain spent to win the GOP nomination, and makes up the lion's share of the roughly $50 million in mayoral campaign ads that have hit the airwaves in the pricey New York media market.
Bloomberg's poll numbers took a minor hit late last year after he persuaded New York's city council to overturn the term limits to allow him to run for a third term this November - but his $33 million outlay has been followed by a massive 33-point advantage among independent voters, according to the new Marist poll.
Bloomberg has captured the endorsement of all three of New York City's major daily newspapers, the Times, Post and Daily News. The Spanish-language daily El Diario La Prensa endorsed Thompson.
The Marist College poll was conducted October 29-November 1, with 1,360 likely New York City voters questioned by telephone. The survey's sampling error is plus or minus 2.7 percentage points.
–CNN Political Producer Rebecca Sinderbrand contributed to this report
Follow Paul Steinhauser on Twitter @psteinhausercnn