According to Smart Politics, when contemplating that race, he told the Sioux Falls Argus Leader "I have always said I would like to come back and run for something there, participate in government."
O'Brien gave no indication in the interview with Carolla about whether he would be interested in Senate seat being vacated in South Dakota by Sen. Tim Johnson (D).
Rounds is now the only announced GOP Senate candidate, and a run in 2014 could give O'Brien that opportunity to face the former governor. But O'Brien could also run for a number of other positions in 2014, including governor.
Currently, two-time House candidate Rick Weiland is the only announced Democratic contender for the Senate seat.
His candidacy came as a surprise, and the two contenders initially considered most likely to run — former Rep. Stephanie Herseth Sandlin and U.S. Attorney Brendan Johnson — have either announced or indicated privately they won't pursue the seat.
Weiland's candidacy hasn't yet been endorsed by Washington Democrats, and he wasn't their first choice. Some Democrats have expressed concerns he's too liberal for the red-leaning state.
While there are indications Democrats are looking for another contender, the bench in South Dakota, after the two leading candidates decided not to run, is short.
--This post was updated at 12:25 p.m.