The first polls have been closing across the United States in one of the most closely watched midterm congressional elections in living memory, which are likely to be seen as a referendum on President Donald Trump's administration.
In Indiana's high-profile US Senate contest, Democratic incumbent Joe Donnelly is seeking reelection against businessman and former legislator Mike Braun.
Four GOP seats in Orange County, including two where the incumbent Republicans retired, were in play, along with three other seats to the north beyond Los Angeles and into the Central Valley. Notably, Michigan Democrats selected a woman for every statewide office on Tuesday's ballot: governor, USA senator, attorney general and secretary of state.
Democrats face a far more hard challenge in the Senate, where they are nearly exclusively on defense in rural states where Trump remains popular.
Rep. Barbara Comstock in the Virginia suburbs outside the nation's capital was among the most endangered Republican incumbents, branded Barbara "Trumpstock" by Democrats. Senate Minority Leader Chuck Schumer is widely expected to retain his post as the Democratic leader.
They need to pick up two dozen seats to claim the House majority. Campaigns unfolded against a backdrop of jarring political imagery, overheated rhetoric and angry debates on immigration, health care and the role of Congress in overseeing the president.
High-profile races for governor in Georgia, Florida and OH also were too close to call.
With control of Congress and Trump's agenda at stake, early voting hit record levels and turnout appeared high across the country.
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The two parties were also tangling in several crucial governors' races, including in Midwest battleground states such as Wisconsin, Ohio, Iowa and MI.
Trump has headlined 30 rallies in two months and packed out arenas of adoring fans.
Results were to continue trickling in through the night, with the last polls closing in Alaska at 0600 GMT Wednesday.
A man wearing a New York Yankees hat votes during the midterm election at P.S. 140 in Manhattan, New York City, U.S., November 6, 2018. That could help Democrats because younger voters tend to lean their way.
Daniel McAdams, executive director at the Ron Paul Institute, agrees, noting that the Democrats "ran a awful campaign" under the slogan "Trump is racist, vote for me". He was active on Twitter throughout much of the day, blasting out endorsements for Republican candidates and weighing in on the balloting. "The Fox News Decision Desk can now project that Democrats will take control of the House of Representatives for the first time in eight years", tweeted Chief Political Anchor Bret Baier. Failure would leave them unable to check president Trump's power.
The tax law has been particularly problematic for Republicans in New Jersey, where four of five GOP-held seats were being seriously contested. "We usually hope for 200 voters for the entire day, but by 9 o'clock we already have had 69", said Bev Heidgerken, 67, a volunteer at a polling place in Davenport, Iowa. "Do not let their scare tactics frighten you away from the polls".
Sensing that his Republican base favors the hardline stand, Trump has sent soldiers to the Mexican border, threatened to have illegal immigrants shot if they throw stones at the border, and vowed to restrict citizenship rights. Both Republicans Rick Scott in the Senate race and Ron DeSantis in the governor's race hold leads in Florida.
"In this cycle, it seemed as if there was a disproportionately negative reaction among highly educated voters to Trump", he said. A CBS News exit poll offers some clues.
Executive Director for the Center for Responsive Politics Sheila Krumholz commented: "The significance of this election is clear".
Fernando Rivera, a 53-year-old small-business owner in Miami, said he voted for all Republicans because he wants Congress to support Trump and his economic policies.