More voters pick a candidate as U.S. Senate race remains close.

OKLAHOMA CITY - Only eighteen days before the election, Brad Carson (D) regained his lead over Tom Coburn (R) in the U.S. Senate race. The lead, however, is still within the margin of error.

SoonerPoll.com, a public opinion research firm in Oklahoma City, conducted the telephone poll of 300 statewide likely voters Thursday for Fox25 in Oklahoma City and KSWO in Lawton showing Carson with 43.3%, Coburn with 40.6%, 2% for Independent Sheila Bilyeu and 14% undecided. The survey had a margin of error of 5.7%.

The week since the last Senate debate has given voters a chance to reflect and make their choices. The number of undecided voters dropped seven points to 14%, the biggest move of the week.

This week's poll also marks the first time both candidates are both over 40%. Carson gained 3.5 points this week, while Coburn gained 1.4.

In the last week, Brad Carson received an endorsement from former Oklahoma football coach Barry Switzer, who also supported Governor Brad Henry two years ago.

Both sides have released ads accusing the other of "flip-flopping" on the issues. As one of the most watched Senate races in the country this year, both the Republican and Democratic Senatorial Campaign Committees have thrown considerable support behind their respective candidates.

Meanwhile, questions over Dr. Coburn's Medicaid billing has remained an issue since surfacing more than three weeks ago.