Missouri's GOP Senate primary might still include a senior member of the state's congressional delegation.

Reps. Sam Graves (R) and Jo Ann Emerson (R) have both passed on challenging Sen. Claire McCaskill (D). But six-term Rep. Todd Akin (R) won't "discount" making a run.

Republicans have been watching with some trepidation as several well-known candidates flirted with nomination bids. A contentious primary could benefit McCaskill, who admits she is the "underdog" in her reelection contest. The GOP field so far only includes attorney Ed Martin and former state Treasurer Sarah Steelman.

A new survey by Public Policy Polling shows Akin essentially tied with McCaskill, while the Democrat leads Steelman 45-42 and tops Martin, a former congressional candidate, 46-40. In a possible match up with former ambassador Ann Wagner (R), McCaskill would win 45-36, according to the survey of 612 Missouri voters. The March 2-6 poll's margin-of-error was plus-or-minus 4 percent.

With that in mind, Akin said he won't rule out joining the fray.

"I haven't discounted it," he told The Ballot Box on Tuesday night. "Some things you sort of put on your problem shelf and you know you're going to deal with it at some time. It's just one of those things that I've got to work through.

"It's obviously a big decision," he added. "With 10 years of seniority here, work is very interesting."

Akin's 2nd district includes suburban St. Louis and could provide a strong base from which to run statewide. The future shape of that district, however, is one of the factors weighing on his decision making.

"I'm focused on redistricting right now. It's a hot topic, and it's very fluid at this point," Akin said. "It's got most of our attention right now."

Missouri is set to lose a congressional seat through reapportionment.

The congressman said he hasn't yet talked to National Republican Senatorial Committee Chairman John Cornyn (Texas) about a possible run.

"When I take the problem off the problem shelf," said Akin, an engineer by trade, "I'll try to find out what's the right thing to do.

"I feel a lot of concern about the nation right now and the situation with the budget. All of those things kind of factor into the right thing to do."