OKLAHOMA CITY - Congressman James Lankford and former Oklahoma House Speaker T.W. Shannon share a nearly even lead in the Republican primary for U.S. Senate, according to a News 9/News On 6 poll.

The survey of 580 likely Republican voters shows 33.8 percent favor Lankford, while 31.9 percent support Shannon.

Remaining candidates had single digit support in the poll, including former state senator Randy Brogdon (4.5 percent), college professor Kevin Crow (1.7 percent), paramedic Jason Weger (1.5 percent), businessmen Eric McCray (0.6 percent) and Andy Craig (0.6 percent). One-quarter of respondents said they are undecided.

Candidates are running to fill the last two years of Sen. Tom Coburn's term. Coburn's sudden retirement announcement in January has already played a role in the election, said Bill Shapard, CEO of SoonerPoll.com.

"Nobody really had an opportunity to put together an operation to prepare for his retirement," explained Shapard.

"You're looking at a fresh start of seven candidates with very little money raised, very little name recognition and that's the reason why we're seeing such a close race among at least the two leaders right now."

Shapard predicts the frontrunner will fluctuate as undecided voters choose their candidate. He also expects Lankford and Shannon to campaign heavily in Tulsa and Oklahoma City.

"This race will be won on either end of the Turner Turnpike. Oklahoma City and Tulsa dominate in terms of Republicans in this state, so both are going to have to do well in both markets to be successful," Shapard said.

Lankford has a 41-point lead over Shannon among voters in the 5th District he currently represents, which includes much of Oklahoma City, according to the poll. Cross tabulations indicate Lankford with 59.4% and Shannon with 18.7% in the 5th district.

However, the poll shows Shannon has a 26-point lead over Lankford in the 1st District, which includes Tulsa. Shannon has 39.9 percent and Lankford has 14 percent in the 1st District, according to cross tabulations.

A candidate needs to get more than 50 percent of the votes cast in the June 24 primary to avoid a runoff. An outright winner could emerge in the primary if the bottom five candidates fail to get more than 14% of votes cast, Shapard said. The winner of the Republican primary will meet a Democrat and Independent challenger in the Nov. 4 general election.

SoonerPoll conducted the survey between May 5 and May 10. Respondents were selected at random using landlines and cell phones. Results were weighted by gender, age, cell phone/landline collection and Congressional district, then stratified using a model of previous primary elections. The poll has a margin of error of plus or minus 4.07 percentage points.