"Tonight is the beginning of the next chapter in our quest to get Missourians back to work," Spence told supporters in St. Louis. "We can and must do better as a state."
With 99 percent of precincts reporting, Spence, 54, won with 60 percent of the vote. Kansas City lawyer Bill Randles, 49, had 16 percent; anti-cloning activist Fred Sauer, 67, had 15 percent; and John Weiler, 60, had 9 percent.
Nixon faced nominal opposition in the Democratic primary, winning 86 percent of the vote.
In the Republican lieutenant governor primary, two-term incumbent Peter Kinder edged Brad Lager after one of the summer's most expensive and negative campaigns. Kinder won with 44 percent to Lager's 42 percent.
Lager, a two-term state senator from Savannah, Mo., used statewide TV ads to attack Kinder for his repayment of more than $54,000 to the state to cover hotel expenses that coincided with social events.
Kinder responded by slamming Lager over his work for a company that has benefited financially from federal health care reform.
With 99 percent of precincts reporting, Schoeller, the speaker pro tem of the Missouri House, had 35 percent to 34 percent for Sen. Scott Rupp and 30 percent for Sen. Bill Stouffer. Kander faced nominal opposition in the Democratic primary.
Ed Martin defeated Adam Warren in the GOP attorney general primary. This fall he will take on Democratic incumbent Chris Koster, who was unopposed in the primary.