WASHINGTON  The Democratic presidential race has become a cliffhanger as a new USA TODAY/Gallup Poll on Sunday showed Barack Obama wiping out Hillary Rodham Clinton's double-digit national lead just before coast-to-coast contests on Tuesday.

The pair stood at Clinton 45%, Obama 44% in the latest snapshot of the volatile race. Republican John McCain also surged in the poll, posting a decisive 42%-24% lead over Mitt Romney. Mike Huckabee trailed at 18%.

McCain greeted the news cautiously. "We'll see how the votes go. We'll keep working," he said.

With a celebrity cast and some Super Tuesday states too close to call, interest was high. Seven in 10 people in the poll said they were paying "quite a lot" of attention — up from 58% at this point in 2004, during another high-interest wartime race.

The Wednesday through Saturday poll of adults nationwide came after Rudy Giuliani left the GOP race and Democrat John Edwards' exit set up a Clinton-Obama clash.

Obama strategist David Axelrod said Clinton is "the greatest brand name in Democratic politics." Still, he said, the Illinois senator has made good progress and "there's a powerful, powerful mood for change in this country."

Obama has ridden a wave of momentum since a landslide win Jan. 26 in South Carolina. On Sunday, he ran a TV ad during the Super Bowl on local Fox stations in 23 states. Building on a series of Kennedy family endorsements, he received support from California's first lady, Maria Shriver.

Clinton's lead faded over two weeks during which Obama advertised heavily and her husband, former president Bill Clinton, took heat from fellow Democrats for attacking Obama. "We have a strong and broad coalition that I think will give us significant delegates and victories on Feb. 5," Clinton adviser Mark Penn said.

In the poll, Clinton led Obama 48%-42% among women, compared with 50%-31% two weeks ago. He reversed her slight lead among men, and completely erased her 21-point advantage among people ages 35 to 64.

Whites backed Clinton 49%-39%, while blacks backed Obama 63%-25%. Both racial gaps were higher than two weeks ago.

McCain, who has been strong among independents and moderates, beat Romney 41%-26% among Republicans or independents leaning Republican and 38%-28% among conservatives. Romney spokesman Kevin Madden said national polls "tell you very little" about state contests.

The poll's margin of error is +/—4 percentage points for 867 Republicans and adults leaning Republican, and +/—3 percentage points for 985 Democrats and adults leaning Democratic.

Contributing: David Jackson in Fairfield, Conn., and Andrea Stone in Glen Ellyn, Ill.