McMahon's main competitor, U.S. Rep. Rob Simmons, garnered enough votes to force a Republican primary this summer. Money manager Peter Schiff did not, although he could go the petition route.
McMahon's big win follows a controversial week. She admitted that her campaign fed a story to the New York Times about Democratic Senate nominee Richard Blumenthal. The story claimed Blumenthal lied about his military service during Vietnam.
The candidates are fighting to fill the U.S. Senate seat being vacated by Chris Dodd.