But other high-profile contests have yet to be decided.
Democratic Sens. Joe Manchin in West Virginia and Tammy Baldwin in Wisconsin won re-election. Bill Nelson hoping late votes in Democratic counties could narrow his slim deficit to his challenger, the outgoing Gov. Rick Scott. Democratic congressional leaders and candidates have vowed on the campaign trail that their party will protect Americans with pre-existing conditions, while warning that Republicans will not.
There was another blow for Democratic morale as Texas Sen. The deeply conservative state features a strong challenge by Democrat Beto O'Rourke to unseat U.S. Senator Ted Cruz. Incumbent Democrat Tom O'Halleran's race moved from "Likely Democrat" to "Lean Democrat", as the freshmen member continues to defend a seat in a district President Donald Trump narrowly won in 2016. Fundraising reports from the third quarter of 2018 cemented those fears as Democrats outraised Republican opponents in competitive House races.
AP VoteCast also showed a majority of voters considered Trump a factor in their votes.
The campaign unfolded against a backdrop of heated rhetoric and angry debates on immigration, health care and the role of Congress in overseeing the president. His connection with his most loyal fans remains so intense that some pundits believe he could help the GOP pull off a surprise.
The early exit polls are most useful in figuring out which campaign messages resonated with voters. Basically, what happened was the same slight error - the marginal underrepresentation of white working class voters favouring Trump - was replicated in a number of key districts located in states with large numbers of electoral college votes. "They're doing not bad", he said. Firstly, in a broad sense, many see the midterms as a referendum on the performance of the sitting president, so poor performance for the Republicans could be an ominous sign of what's to come in 2020. For a long time there, Democrats felt good about Tennessee.
Campaigning in Ohio, Trump declared that "everything is at stake" as he sought to bolster the campaign of Ohio Attorney General Mike DeWine, the Republican candidate for governor.
In suburban areas where key House races were decided, voters skewed significantly toward Democrats by a almost 10-point margin.
News projected Democrats would hold a 229-206 House majority, taking over control from the Republicans for the first time in eight years.
At 7 p.m., most polls in New Hampshire and Vermont close, but the contests in those states are only mildly interesting.
Democrats, whose very relevance in the Trump era depended on winning at least one chamber of Congress, were laser-focused on health care as they predicted victories that would break up the GOP's monopoly in Washington and state governments.
In recent days, Mr Trump has accused Democrats of being "radical socialists who want to model America's economy after Venezuela", and said they wanted to invite "caravan after caravan of illegal aliens into our country".
"He is really angry at Ryan", one source said on "everything". Several have history making potential, especially in Florida where Tallahassee Mayor Andrew Gillum, a Democrat, is trying to become the state's first African-American governor in an ill-tempered duel with former Rep. Ron DeSantis, a Trump favorite.
Goodstein, however, still believes that Trump "is uniquely disfavored" and numerous voters who strongly disapprove of Trump will take to the polls, allowing the Democrats to regain the House of Representatives. But they failed to win the governor's mansions in OH and Florida, two big states where they'd had hopes for marquee victories.