Republicans now hold 33 governorships and 65 legislative chambers, with Democrats controlling 31 and two being tied, according to the nonpartisan National Conference of State Legislatures (NCSL), which does not include Nebraska's nonpartisan, unicameral legislature in its count. Senate Minority Leader Chuck Schumer is widely expected to retain his post as the Democratic leader.
The party needed a net gain of 23 seats to break the Republicans' eight-year hold on the House and place a check on President Donald Trump.
The Republican party now has majority in both the Senate and the House and Trump and his team left no stone unturned to campaign in favour of his Republican party.
Ahead of the election, both parties claimed that the emotionally charged debate over Kavanaugh's confirmation would motivate their supporters to turn out. There have been a record number of retirements, reducing the built-in advantage incumbents tend to have; record numbers of candidates, especially Democratic women, have run for public office; Democrats won the off-year elections in Virginia and New Jersey; they won or fared better than expected in special elections across the country; there was high primary turnout for Democrats in many states; and there is very high early voting turnout.
There are too many fundamental differences between electoral systems and cycles in the US and Canada for this year's stateside turnout to offer any lessons for anyone hoping to generate similar levels of interest north of the border in 2019, Haussman said.
The Republican Party maintained control of the Senate.
"The contrast in this election could not be more clear".
Record diversity on the ballot may have helped drive turnout.
While men with military backgrounds have always been recruited to run for office, this year's candidates include several female veterans. The House was also getting its first two Muslim women, MA elected its first black congresswoman, and Tennessee got its first female senator.
Three states could elect their first African-American governors, while several others were running LGBT candidates and Muslims.
The poll also showed that health care, a dominant theme of many Democrats' campaigns, was considered the key issue in Tuesday's election, followed closely by immigration.
How close are the elections going to be?
How it would happen: Speaking of small but substantial possibilities, that's what Republicans have when it comes to holding the House.
Former President Barack Obama - on the campaign trail for the Democratic party - said earlier on Monday that "the character of our country is on the ballot".
Trump, as he did throughout the campaign, also blamed the media for sowing division in the country and insisted they were to blame for the scene unfolding in the East Room.
And in Kansas, Democrat Sharice Davids beat a GOP incumbent to become the first Native American and gay woman elected to the House. In Kentucky, one of the top Democratic recruits, retired Marine fighter pilot Amy McGrath, lost her bid to oust to three-term Rep. Andy Barr in the Lexington-area district. In a tweet Wednesday, he referred to the election results as a "Big Victory".
Trump dissected the elections in a combative White House news conference that stretched to almost 90 minutes as he put a defiantly glossy sheen on the mixed midterm results and stressed his party's victories in the Senate.
Republicans paved their path to victory by defeating Democrats Joe Donnelly of IN and Heidi Heitkamp of North Dakota.
Some hurt worse than others.
In traditionally red Texas, popular Democrat Beto O'Rourke is trying to dethrone Senator Ted Cruz, while Republican Pete Stauber might flip a House Democratic stronghold in Minnesota.
More than 60 percent of eligible voters took part in the 2016 vote, when the presidential race was on the ballot.
Two other sources close to the White House said that Trump is already blaming retiring House Speaker Paul Ryan for the loss of the House.
Mr Trump's closing argument has largely focused on fear, warning, with no evidence, that a Democratic takeover would throw the country into chaos, spurring an influx of illegal immigration and a wave of crime. "So, something's happening", Trump said before departing for his final campaign swing Monday. He frequently invoked his upset win in 2016 and tried to recapture that energy in his final rallies, at times relegating the candidates he had traveled to endorse to supporting actors in the theater of a Trump rally.
The president found partial success despite his current job approval, set at 40 percent by Gallup, the lowest at this point of any first-term president in the modern era.
Midterm elections are typically hard for the party in power, but the GOP's hold on power was further weakened by an unusually large number of retirements as well as infighting between conservatives and centrists over their allegiance to Trump. Along with Sherrod Brown, a pro-labor lawmaker re-elected in OH, the four are considered potential 2020 Democratic presidential hopefuls.