Polls closed at 7 pm in the states of Georgia, New Hampshire, South Carolina, Vermont and Virginia, as well as in most of Florida, an hour later than they did in Kentucky and Indiana for Tuesday's midterm elections.
US voters are renewing the entire House of Representatives - 435 seats - along with 35 of the nation's 100 Senate seats and 36 governorships, as well as thousands of local and state posts in elections that are widely considered to be referendum on the presidency of Donald Trump but also on the performance of the Republican Party that has backed him and which controls both houses of Congress.
In the states where the polls are now closed, the Senate race in Indiana stands out, with Democrat Joe Donnelly fighting to retain his seat against Republican Mike Braun, while Florida and Georgia have garnered nationwide attention for their gubernatorial battles, as well as the contest for one of Florida's Senate seats, where Democratic long-time incumbent Bill Nelson is being challenged by the state's Republican governor, Rick Scott.
In Georgia, meanwhile, Democrat Stacey Abrams is vying with Republican Brian Kemp to become the first African American woman in history to lead a state.
The heavy political polarization that has developed in the US during the presidency of Trump, who arouses similar - although quite opposite - levels of passion among both Democrats and Republicans, has been pointing for some time to relatively heavy voter participation.
Prognostications from voter surveys are mixed but the prevailing wisdom seems to be that the Democrats will - in all likelihood - retake control of the House but fail to obtain control of the Senate, where the GOP may even gain a seat or two, further cementing its current narrow 51-49 majority in the upper house.
The Democrats need to win 23 seats to regain their majority in the House, which the Republicans have controlled since 2011.
Trump, who will complete his second year in the White House in January, has campaigned non-stop in the midterm elections, focusing on states where his Republican Party has a chance to pick up seats, especially in the US Senate.
The president has touted his administration's economic policies, which have resulted in strong economic growth, record job creation and low unemployment.
Historically, however, the party in power generally has lost seats in Congress in the midterm elections.