Rep. Steve Stockman (R-Tex.), second from right, is sworn in to office by House Speaker John A. Boehner (R-Ohio) in January.  On Monday, Stockman filed paperwork to challenge fellow Texas Republican and powerful incumbent John Cornyn for the U.S. Senate next year. (Evan Vucci, Associated Press)

The biggest winner from Rep. Steve Stockman's (R-Tex.) last-minute decision to run in a primary against Senate Minority Whip John Cornyn (R-Tex.) might be Doug Centilli.

Centilli, currently chief of staff to Rep. Kevin Brady (R-Tex.), was one of five House Republicans who were quick enough to file for Stockman's seat before the filing deadline Monday night. He faces a field of relative political unknowns -- certainly a less-formidable field than likely would have existed had Stockman not waited until the last minute.

The field also includes Kim Morrell, who finished seventh in the 2012 primary with less than 4 percent of the vote, along with former state Senate candidate Dave Norman and two political unknowns, John Amdur and Phil Fitzgerald.

Stockman's 36th district was created in the latest round of redistricting and is strongly conservative, meaning the GOP primary is likely the ballgame.