Hartzler was expected to face a tough challenge from Hensley, the Cass County prosecutor. New 2012 boundaries expanded the district into central Missouri, including Boone County -- traditionally a strong county for Democrats.
With 100 percent of the precincts reporting, Hartzler had 177,095 votes to Hensley's 104,066, winning 60 percent to 35 percent.
The 4th District race was considered the most competitive of Missouri's eight House races.
"I've worked very hard to listen to the people and to fight for them," Hensley said. "And people know that."
Hartzler, 52, has been a reliable vote for Republican positions in the House. She campaigned on proposals to reduce the federal deficit and cut federal regulations, and she has argued repeatedly for increasing defense spending. Missouri's 4th District includes Whiteman AFB and Fort Leonard Wood.
Hensley, 53, campaigned on her experience as a lawyer and prosecutor. She hoped to draw Democratic votes in Columbia, home to the University of Missouri.
Hartzler was able to spend more on her race than Hensley. Through Oct. 17, Hartzler raised $1.35 million for her campaign, federal records showed, while Hensley had raised $790,501 through the same period.
It's the fourth time the two have faced each other for the House seat. Despite redistricting and a closer-than-expected 2010 result, Cleaver always was considered the favorite in his campaign for re-election.
With roughly half of the votes counted, Cleaver led by a 2-to-1 ratio.
The incumbent's financial problems were an issue in the race. Cleaver is being sued by Bank of America, which claims the former Kansas City mayor defaulted on a $1.5 million loan to buy a car wash. He has said the sale of the car wash is pending.
With 87 percent of precincts reporting, Graves led 65 percent to 32 percent.
Graves had dramatically more money to spend than Yarber.
The Democrat raised less than $60,000 through mid-October, while Graves collected more than $1.3 million.