With 98 percent of precincts reporting, Blunt easily led a field of nine Republican candidates, pulling 71 percent of the vote, returns posted Tuesday on the Missouri secretary of state's Web site indicated. Carnahan had 83.7 percent of the vote against two other candidates for the Democratic nomination.
Blunt and Carnahan will meet in November to determine a successor to retiring Republican Sen. Christopher "Kit" Bond.
Proposition C, a ballot question asking whether Missouri should reject the new U.S. healthcare reform law, was passing by 71.5 percent to 28.5 percent, with 98 percent of precincts reporting.
Legal experts said the question of whether Missourians can opt out of the federal health insurance mandate would be settled in court.