Republican Bob Corker and Democrat Harold Ford Jr. remain neck-and-neck in the race to replace Bill Frist in the U.S. Senate with two weeks left before the Nov. 7 election, a new poll shows.

Of 625 likely voters surveyed by Mason-Dixon Polling & Research for The Commercial Appeal, the Chattanooga Times Free Press and MSNBC, 45 percent support Corker while 43 percent said they'd vote for Ford.

In a poll by the same company three weeks ago, Ford held 43 percent and Corker had the support of 42 percent.

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The poll was conducted Oct. 18-20 and has a sampling error margin of plus or minus 4 percentage points, which leaves the race in a statistical tie.

Democrats must pick up six seats in the Senate to gain a majority, and further polling from Mason-Dixon indicates Republicans trail in the six closest races except in Tennessee and Virginia.

"Tennessee and Virginia are going to be the two states that, right now, are going to control the outcome in the Senate. If the Republicans can win both, they'll have a 50-50 tie and Vice President Cheney breaks the tie. But if they lose one or the other, it looks like chances are pretty good they'll lose control of the Senate," said J. Brad Coker, managing director of Mason-Dixon Polling & Research.

The Republican National Committee has spent hundreds of thousands of dollars recently on TV advertisement in an effort to make Tennessee a "firewall" against a Democratic takeover of the Senate.

The survey concluded Thursday, the day before the RNC began airing an ad statewide which has a hunter saying Harold Ford wants to take their guns away and a white woman saying the black congressman attended a party sponsored by Playboy. She then winks as she invites him to call her.

Vanderbilt University political science professor John Geer said Ford remains close to Corker, despite a barrage of negative attacks on him.

"This poll helps me understand why the national party launched that over-the-top ad against Ford using the blonde at the end saying 'Call me.' That ad, using sexual innuendo, is run by a party and a candidate when they are behind," said Geer, author of a newly published study of negative attack ads in presidential campaigns.

Ford senior campaign adviser Michael Powell said the poll confirmed something the Ford campaign has known.

"The race is a dead heat," he said. "We are well-funded and well-organized and we are confident that in the last two weeks, Tennesseans will reject Bob Corker's negative personal attacks and vote for hope over fear, the future over the past and change over more of the same."

Corker spokesman Todd Womack said the poll "reflects what we're seeing every day on the campaign trail — that we have the momentum. Congressman Ford's campaign is cash-strapped, in disarray and has peaked. Bob Corker is a real Tennessean who has spent his life using bold solutions to solve complex problems."

The poll also found that incumbent Gov. Phil Bredesen holds a 62 to 27 percent lead over Republican challenger Jim Bryson.