Missouri state Sen. Bill Stouffer on Wednesday formally kicked off his campaign for the Republican nomination to take on veteran Democratic Rep. Ike Skelton in 2010.

GOP officials are vowing to vigorously challenge Skelton in the west-central 4th District for the first time in many years. Stouffer’s official campaign launch marked the latest step in what is shaping up as a busy field for the August Republican primary: Former state Rep. Vicky Hartzler and computer security consultant James Scholz have also announced bids to challenge the 17-term incumbent.

Stouffer, a farmer who is in his second four-year term in the Missouri Senate, planned a morning announcement event in Blue Springs, which is near Kansas City in the far western part of the district. He also planned to declare his candidacy later Wednesday in Marshfield, which is in the far southern part of the district, and on Thursday in Jefferson City, Missouri’s state capital, at the district’s eastern end.