However, final results from at least five of those contests may not be available for days, and in some cases, months.
With public disapproval of President Donald Trump weighing on Republicans across the country, voters are deciding whether to end the political careers of embattled Republican senators, including Trump ally Lindsey Graham of South Carolina and moderate Susan Collins of Maine, among others.
In total, 12 Republican-held seats and two Democratic-held seats are in play, based on a Reuters analysis of three nonpartisan U.S. elections forecasters - the Center for Politics at the University of Virginia, the Cook Political Report and Inside Elections.
McConnell was among a dozen incumbents from both parties to be declared early winners, as expected. McConnell overcame a challenge in Kentucky from Democrat Amy McGrath, a former U.S. Marine Corps fighter pilot who out-fundraised McConnell by $40 million but was unable to overcome the state's Republican sway.