TULSA, Oklahoma - Polls open early Tuesday morning in Oklahoma's primary election. A hotly contested seat is the race to replace Senator Tom Coburn.

The Republican front-runners each had stops in Tulsa Monday. Congressman James Lankford, former State House Speaker T.W. Shannon and former State Senator Randy Brogdon all campaigned within a mile of each other in Southeast Tulsa. It was the candidates' last drive to sway voters before they head to the polls.

Republicans vying for retiring Senator Tom Coburn's seat hit Tulsa's breakfast joints and lunch lines to sway last minute voters. Former Oklahoma House Speaker T.W. Shannon got on the trail early.

"We started out at 5:15 this morning, and we're going to go up till the very end till the polls close," Shannon said. "You know, people deserve the next United States Senator who's going to earn their vote."

Congressman James Lankford says he's treating the run up to election day like a job interview.

"So, I'm in this long job interview, I'm going to interview as many people as possible they're going to decide who they're going to hire tomorrow during the election time and then we'll go from there," he said.

Former State Senator Randy Brogdon says his push to election day is all about getting support by going door-to-door across the state.

"I don't take money from the tall building crowd and from special interests. My support comes from the grassroots, the Tea Parties and I'm very proud of that," the Owasso Republican said.

Exclusive polling data shows Lankford ahead, but the two-term congressman isn't calling the race in his favor.

Shannon says his campaign has terrific momentum.

"The poll that's going to matter is the one tomorrow night," Representative James Lankford said. "We've shown we're in the lead for a very, very long time; we're very humbled by that, but the issue really people have to decide who they're going to trust."

"We started out literally 37 points behind and when you're running against an establishment candidate that's got support from Washington, D.C., we knew we were starting out as the underdog," Shannon said.

Early voting has ended Monday evening. Polls open Tuesday bright and early starting at 7 a.m.