Carson maintains small lead as race tightens.

OKLAHOMA CITY -- Tom Coburn (R) may have made up some ground over the last week, but remains in a tight battle with Brad Carson (D) and within the margin of error to replace retiring Senator Don Nickles next year.

SoonerPoll.com, a public opinion research firm in Oklahoma City, conducted the telephone poll of 394 statewide likely voters for Fox25 in Oklahoma City showing Carson with 39.8%, 37% for Coburn and 23.3% undecided. The survey had a margin of error of 4.9%.

"The poll presents several weaknesses of both candidates and could very well explain why the race is so tight," Bill Shapard said, President of SoonerPoll.com. "Coburn is in a 6% deficit among women voters yet only leads with men voters by less than 2%. Carson, on the other hand, is trailing Coburn among Independent voters by more than 38 points."

Both candidates dominate within their own party with Coburn receiving 63% of Republican support and Carson backed by 59% of Democrats. Almost an equal number of Republicans and Democrats, 22% and 23% respectively, remain undecided.

Interestingly, the percentage of undecided voters has steadily climbed since the first poll was conducted, signaling more and more voters are wanting a little more time to sort out all of the rhetoric in the race.

Coburn stepped up his television advertising this week featuring Carson's photo in a jigsaw puzzle. The ad focuses on comparing Carson's voting record in the U.S. House to more liberal members of Congress and distancing Carson's votes from President Bush. To date, no significant airing of ads on behalf of Coburn have begun from Republican organizations or the Club for Growth, who spent hundreds of thousands on Coburn in the Republican primary.

The Democratic Senatorial Campaign Committee continues to pour more money into television ads on behalf of Carson. A new ad, featuring Dr. Coburn's head on a jack-in-the-box, focuses on his recent controversial comments while defining Coburn as a far-right extremist.

Still trying to capitalize on Coburn's blunt remarks, Carson himself unveiled a new ad that centers on the 'good vs. evil' comment made by Coburn at a Tulsa debate.