Monday's poll had Coburn within 2 percentage points of Carson and also within the poll's margin of error of 4.5 percentage points.
On Sept. 27, Carson had a 5-percentage-point advantage over Coburn in the weekly poll conducted by Wilson Research Strategies.
Coburn gained ground because Carson, D-Claremore, lost the support of several moderate Republicans, said Chris Wilson, president of the Virginia-based polling company.
In Monday's poll, 54 percent of moderate Republicans backed Coburn, while Carson's support had fallen to 19 percent among the group. Just the week before, Carson had 41 percent of the support among moderate Republicans.
Of all the registered voters polled, 43 percent supported Carson and 41 percent said they would vote for Coburn, R-Muskogee.
The poll is the fifth of nine polls leading up to Election Day on Nov. 2. The poll of 500 registered Oklahoma voters who are likely to cast a ballot was commissioned by NEWS 9 and taken by telephone from Friday through Sunday.
Most of the poll was conducted before a nationally televised debate Sunday between Carson and Coburn on NBC's "Meet the Press," Wilson said.
The election has garnered national attention because at stake is control of the Senate, where the GOP has a majority of 51 members. Carson and Coburn are vying to succeed retiring U.S. Sen. Don Nickles, R-Ponca City.
Other results in Monday's poll showed President Bush lead over U.S. Sen. John Kerry, D-Mass, grew from about 25 percentage points in last week's poll to 30 points among Oklahomans polled.
Oklahomans also continued to support the state questions establishing a lottery, legalizing new electronic gambling machines at horse-racing tracks and tribal casinos, a new cigarette tax and amending the state constitution to outlaw gay marriage.
Those numbers could change significantly between now and Nov. 2, Wilson said.
"These state questions, because they're not defined, they could really be all over the map between now and Election Day," Wilson said. "The numbers kind of harden up a little bit with Republicans and Democrats as they start to push their message and both sides start to communicate."
