In a surprise move at the filing deadline, U.S. Rep. Steve Stockman, R-Friendswood, has decided to run against U.S. Sen. John Cornyn in the March GOP primary.

Stockman, who had already filed for re-election in Congressional District 36, had to withdraw from that race to seek Cornyn's seat. He joins at least eight other Republicans vying to replace the senior senator from Texas.

Political observers had seen Cornyn as the likely winner of the March 4 primary, since most of the other candidates are not well known.

According to POLITICO, Texas GOP chair Steve Munisteri said only 20 minutes before the filing deadline that he was “not expecting any recognizable names or people with substantial resources running aside from the senator.”

Stockman, 57, served in the U.S. House of Representatives from 1995 to 1997. The deeply conservative Stockman returned to the House this year and began to shake things up.

He called for the impeachment of President Barack Obama, who he likened to Saddam Hussein, and urged the U.S. to withdraw from the United Nations. He also fought the administration on proposed gun regulations, which he said were unconstitutional.

Some supporters of the other senator from Texas, Ted Cruz, have been angry with Cornyn since he failed to support Cruz’s procedural motion to end funding for Obamacare.

That move led the Senate Conservatives Fund to blast Cornyn as a “turncoat” and enraged conservatives back home, according to POLITICO.

However despite some growing opposition to Cornyn -- who some say is not conservative enough -- Stockman had just $32,000 cash-on-hand as of the last filing in the coffers of his re-election campaign for District 36, and is more than $160,000 in debt.

He is likely to see more donations now that he is running for senator, but has catching up to do with Cornyn, who already has $7 million in his campaign fund.

Stockman recently came under fire after a Houston Chronicle investigation revealed that he violated federal ethics laws by failing to disclose a series of business affiliations, while providing no details about the business he said was his only source of income.

Other challengers in the Republican primary include attorney and activist Linda Vega, Liberty businessman Dwayne Stovall and Tea Party candidates Reid Reasor and Chris Mapp.

In the Democratic primary, Dallas dentist David Alameel faces El Paso lawyer Maxey Scherr and former GOP House candidate Michael Fjetland of Houston.

John Amdur of Houston and Phil Fitzgerald of Hull have filed for Stockman’s seat in District 36.

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