But their algorithm has also given them an equally strong chance of retaining control of the Senate.
Tensions have been running high ahead of the midterms, with Democrats calling to shed civility and Republicans branding their opponents left-wing socialists.
On the eve of the mid-term elections, Democrats continue to hold a double-digit lead over Republicans in a generic congressional ballot among likely voters, according to a new CNN Poll conducted by SSRS. Marsha Blackburn triumphed in Tennessee. Pelosi says that as few as 25,000 votes nationwide could swing the results. He was defeated by Democrat Debbie Mucarsel-Powell.
About a half-hour later, he gave GOP Rep. Peter King a shout-out.
Whether they flip the House or not, Democrats are still expected to gain seats in the chamber, given the favorable political environment for Democrats. What was not normal was that Menendez had been indicted on corruption charges and escaped with hung jury. Democratic gubernatorial candidate Andrew Gillum is narrowly trailing his challenger Rep. Ron DeSantis. That could mean an impasse on issues including immigration, gun regulations and health care. "I'm not saying you're a racist, but the racists think you're a racist".
Addressing his supporters, he said, "The key is you have to go out to vote because in a sense I am on the ticket".
The outcome of the midterms will also mark the culmination of a bitter partisan battle for control of Congress and set the stage for the 2020 elections, where an expansive field of Democratic presidential candidates is expected to challenge Trump after his first term in office.
They decide which members of the United States Congress, made up of the Senate and House of Representatives, are elected for another four years. Seven seats are now vacant.
In the final stretch, Mr Trump hardened his rhetoric on issues that appealed to his conservative core supporters, issuing warnings about a caravan of Latin American migrants headed to the border with Mexico and condemnations of what he called U.S. liberal "mobs".
As Election Day neared, it became increasingly clear what the final messages were from Republicans and Democrats.
The party needed a net gain of 23 seats to break the Republicans' eight-year hold on the House that began with the tea party revolt of 2010. Heidi Heitkamp in North Dakota, CNN projected.
In Indiana, Trump-backed businessman Mike Braun defeated Democratic incumbent Joe Donnelly. Nelson, 76, faced outgoing Republicans Gov. Rick Scott, who poured over $50 million of his own fortune into his campaign, the most in the U.S. More than two-thirds rate the economy as good, compared to 36 percent only two years ago.
Democratic Sens. Joe Manchin in West Virginia and Tammy Baldwin in Wisconsin won re-election.
To seal the win, the GOP drew backing from hard-right voters in rural, deep-red states, where Trump's nativist, racially tinged rhetoric and insult-laden discourse were as stirring for some conservatives as they were infuriating to liberals elsewhere. "They ignored the consultants who said they should cover up their tattoos and smile more, and they ignored the powerful men of the Republican Party who never took them seriously anyway". A slow-moving caravan of thousands of Central American migrants trekking to the USA has served as ready fodder for Trump's diatribes for border security and immigration reform, and a roaring economy has helped the GOP foster confidence in their leadership.
"I think everyone was bracing for any possible, insane scenario to show itself tonight but it basically looks like the baseline consensus forecast was correct", said Michael Purves, head of equity derivatives strategy at Weeden & Co, New York.
Election workers assist would-be voters at First Ward Creative Arts Academy on November 6, 2018, in Charlotte, North Carolina.
A Trump supporter in Florida was charged recently with sending pipe bombs to high-profile Democratic critics of the president, and a gunman walked into a Pittsburgh synagogue and shot 11 worshippers dead several days later.
Democrats boasted record diversity on ballots. Ted Cruz in Texas. John McCain (Ariz.) and the retirements of Sens. Jeff Flake of Arizona and Tennessee's Bob Corker, both leaving Congress after accusing Trump of dishonesty and questioning his competence. Donovan was the only Republican representing New York City.
The Republican Senate win was especially significant because that chamber confirms nominations, including for Supreme Court justices and federal judges, a top GOP priority.
Senators Bernie Sanders of Vermont and Elizabeth Warren of MA easily won re-election as they consider bids for the Democratic presidential nomination. A record number of women were running for Senate, House, governorships and state legislative seats. The five-term incumbent broke with his party and voted against the Republican tax bill and the GOP's 2017 effort to repeal and replace the Affordable Care Act.
AP reporter Ben Finley in Norfolk, Virginia, contributed.