"It's not about Democrats and Republicans at this point", she told volunteers in Pima County.
Outside Richmond, one-time tea party favorite Rep. Dave Brat faced an unusually strong challenge from Democrat Abigail Spanberger, a former Central Intelligence Agency operative motivated to run for office after the Republican vote to gut the Affordable Care Act.
The Republicans held on to the Senate and narrowly survived a number of big individual races, including in Florida.
The Democrats also won some of the high-profile governor's race including Kansas, Illinois, Michigan and Minnesota.
Fundraising, polls and history were not on the president's side.
"Everything we have achieved is at stake", Mr Trump declared in his final day of campaigning.
Almost two-thirds said Trump was a reason for their vote. "Certainly we feel good about where things are headed".
"She forecasts Democratic victories across the country, but with a small overall margin of victory".
According to The New York Times, amid signs that the nation's deep political and cultural divisions that lifted Trump in 2016 may only be deepening, "rural voters were breaking sharply" with their counterparts in the suburban districts and metropolitan areas, as turnout soared in a midterm election that came to serve as a national referendum on the president.
A divided Congress is likely to extend the heated battles of the 2018 campaign into the presidential election in 2020. And only twice in the past eight decades has the president's party picked up House seats in the midterms.
It comes as the Republicans have held on to the Senate after key victories in Indiana, Texas and North Dakota.
Americans voted for all 435 seats in the House, and female candidates stole the spotlight in an election cycle that had been billed as the Year of the Woman. A few had already won re-election Tuesday, including in Ohio, Pennsylvania, West Virginia and Wisconsin.
United Kingdom business bosses add voices to call for new Brexit vote
The open letter warns that Theresa May's final exit deal will push Britain towards "a destructive hard Brexit". More than 70 business leaders have signed a letter calling for a People's Vote on the UK's Brexit deal.
"The American people want peace; they want results; they want us to work for positive results for their lives", Pelosi said at an election night celebration with top House Democratic leaders.
He and the first lady were to host an evening watch party for family and friends.
They also could force Trump to scale back his legislative ambitions, possibly dooming his promises to fund a border wall with Mexico, pass a second major tax-cut package or carry out his hardline policies on trade.
With a House majority, Democrats will have the power to investigate Trump's tax returns and possible conflicts of interest, and challenge his overtures to Saudi Arabia, Russia and North Korea. Others have pledged to pursue impeachment, although removal from office is unlikely so long as the GOP controls the Senate.
Trump's Republican coalition is increasingly older, whiter, more male and less likely to have a college degree. Like other Democrats across the country, Spanberger emphasized protecting people with pre-existing conditions from being denied coverage or charged more by insurers.
Republicans won Congress in 2010 and retook the Senate in 2014.
Pelosi, confident of Democrats winning the House, is hoping for a "decisive" majority, some 230 seats, and optimistic she will again be elected speaker.
The demographic divides were coloring the political landscape in different ways.
Miloscia, a former Democrat turned moderate Republican, on Tuesday trailed Democrat Claire Wilson, president of the Federal Way School District Board, by about 6 points.
Pelosi said the election Tuesday was about more than Republicans and Democrats.
In the Senate, centrist Democrats from states that Trump won In 2016 such as Joe Donnelly In IN and Heidi Heitkamp In North Dakota were replaced by conservative Republicans who may credit their victories to the president.
Historically, the party in power loses several seats during the first midterm election of a new president, particularly if his national job approval ratings are low.
Democrats boasted record diversity on ballots.
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