CNN

Brownback is set to wrap up a 4-day bus tour of Iowa Thursday.

WASHINGTON (CNN) - Reaffirming his commitment to win the Iowa straw poll later this summer, Republican presidential hopeful Sam Brownback announced he will officially open a campaign office in Ames, Iowa Thursday.

Ames, the sight of the non-binding August straw poll, is the Kansas senator’s last stop in a 4-day, 27-town bus tour of the crucial early caucus state.

"Iowans agree that we need to rebuild our families and renew the American culture," Brownback said in a statement. "Coming from a small town and rural background myself, I am committed to visiting small-town Iowa just as much as the larger cities. You can’t win the presidential nomination if you don’t compete in Iowa, and you can’t compete in Iowa unless you participate in the Ames straw poll."

Fellow GOP candidates Rudy Giuliani, the former New York City Mayor, and Sen. John McCain of Arizona, have announced they will not participate in the straw poll, a state GOP fundraiser that has traditionally been viewed as an early test of strength and organization in the Hawkeye State.

– CNN Ticker Producer Alexander Mooney