Wichita ? Republican Rep. Todd Tiahrt plans to take the last step he needs to take to make his Senate candidacy official.

His campaign says he plans to file for the office Thursday. He plans to fill out the necessary paperwork at 10 a.m. at the Sedgwick County Courthouse.

When those papers and a fee of almost $1,700 get to the secretary of state’s office in Topeka, it will guarantee Tiahrt a spot on the ballot for the August 2010 GOP primary.

Rep. Jerry Moran also has filed for the Republican nomination.

They’re seeking the seat held by Republican Sen. Sam Brownback, who is running for governor in 2010.

Tiahrt represents the 4th District of south-central Kansas. Moran represents the sprawling 1st, which includes western Kansas.