Des Moines, Iowa ? Sen. Sam Brownback of Kansas is expected to end his candidacy for the White House as early as today, narrowing the field of Republican presidential contenders, GOP sources said Thursday.

Only a week ago, Brownback had indicated that he would have to finish no lower than fourth in Iowa’s caucuses for him to continue his campaign in New Hampshire and other states.

The senator also earned some of his biggest media coverage a week ago when he appeared with Democratic contender Sen. Joe Biden of Delaware in Iowa. The two made an unusual bipartisan joint appearance to push a plan for a division in Iraqi governance as a way to get U.S. troops out of the country.

Brownback was elected to the Senate in 1996 to replace another presidential contender from Kansas, Republican Bob Dole, who was defeated by President Bill Clinton.

Focusing his campaign on religious conservatives, Brownback had sought a second-place finish to former Massachusetts Gov. Mitt Romney in the limited field that participated in Iowa’s GOP straw poll in August, but finished third behind Romney and former Arkansas Gov. Mike Huckabee. Huckabee, a Baptist minister, also has sought backing from religious conservatives.