But there were setbacks for vocal supporters of former President Donald Trump's claims of election fraud.
According to a Washington Post analysis, nearly 300 Republicans on the ballot for midterms had questioned the validity of the last presidential election -- a figure also highlighted by Democratic President Joe Biden.
By late Tuesday more than 140 of those had won their races, including House and Senate seats, as well as state-level contests, Barron's reported.
Those who capture state offices such as governor and secretary of state will be in positions of power to change election rules to the advantage of their favored candidates.
Vote counting is underway in the US midterm vote that will determine whether Republicans win control of Congress, which would give them the power to block much of President Joe Biden's agenda.
More than 46 million Americans voted either by mail or in-person, according to data from the US Election Project, and state election officials caution that it will take time to count all of those ballots. Control of the Senate might not be not known until a potential Dec. 6 runoff in Georgia.
US midterms occur halfway through a president’s four-year term. They influence how the president’s next two years will go and will affect how easy or difficult it will be to get legislation passed.
MP/PR