Across the fifty states, approximately 56 percent of all upper house seats and 92 percent of all lower house seats were up for election.

Democrats made significant ground in state legislative races, flipping six chambers from the Republicans and winning control of one tied chamber.

Regularly-scheduled elections were held in 87 of the 99 state legislative chambers in the United States; nationwide, regularly-scheduled elections were held for 6,064 of the 7,383 legislative seats.

News sources predicted Democrats would make significant gains in state legislative control, flipping multiple chambers and narrowing Republican majorities in many others.

Democrats flipped over 350 state legislative seats from the Republicans,[5] with Republican flips offsetting their to total net gain to just over 300 seats.

Democrats picked up most of those seats in states where President Trump's approval rating was relatively low.

[7] Additionally the Connecticut Senate went from being evenly divided to a Democratic majority.

[7] Democrats also broke Republican legislative supermajorities in North Carolina,[8] Michigan, and Pennsylvania,[6] and they gained a legislative supermajority in both houses of the California, Illinois, and Oregon legislatures.

Republicans retained control of the Senate, while a cross-partisan coalition of Democrats, Republicans, and independents retained control of the House of Representatives.

All of the seats of the Kansas House of Representatives were up for election in 2018; the Republican-controlled Kansas Senate did not hold regularly scheduled elections in 2018.

Democrats control both chambers, and the governor is a member of the Republican Party.

Democrats hold a veto-proof supermajority in the state legislature.

[6] All of the seats of the Minnesota House of Representatives were up for election in 2018; the Republican-controlled Minnesota Senate did not hold regularly scheduled elections in 2018.

Democrats won control of the House of Representatives, making Minnesota the only state in the country where each major party controlled one state legislative chamber.

Nebraska is also unique in that its legislature is officially non-partisan and holds non-partisan elections, although the Democratic and Republican parties each endorse legislative candidates.

All of the seats of the New Mexico House of Representatives were up for election in 2018; the Democratic-controlled New Mexico Senate did not hold regularly scheduled elections in 2018.

All of the seats of the South Carolina House of Representatives were up for election in 2018; the Republican-controlled South Carolina Senate did not hold regularly scheduled elections in 2018.

Democrats had previously flipped control of the Senate in a 2017 special election.

All of the seats of the American Samoa House of Representatives were up for election.

Members of the House of Representatives serve two-year terms.

Gubernatorial and legislative elections are conducted on a nonpartisan basis in American Samoa.

A portion of the seats of the Northern Mariana Islands Senate, and all of the seats of the Northern Mariana Islands House of Representatives, were up for election.

All of the seats of the unicameral Legislature of the Virgin Islands were up for election.

The Council of the District of Columbia serves as the legislative branch of the federal district of Washington, D.C. Half of the council seats are up for election.

Various states will hold special elections for legislative districts throughout the year.