The election often doesn't end on election night on the West Coast, where a majority of voters cast their ballots by mail or drop them off.
And with competitive congressional races in Washington state and California, the outcome of any close race could take days to determine.
COMPETITIVE RACES TOO CLOSE TO CALL?
Three of Washington state's 10 U.S. House races are being watched nationally as Democrats eye potential gains that could determine control of the chamber. The party needs a net gain of 23 seats nationwide to win back the House. California — where more than 67 percent voted by mail in the primary — has more than half a dozen competitive races in GOP-held districts.
U.S. & World
WHAT DOES ELECTION NIGHT IN A VOTE-BY-MAIL STATE LOOK LIKE?
In a state that doesn't require ballots to be in by election night, like Washington, a significant portion of the vote will not be processed until the day or days after the election.
Washington state's 39 counties all post their initial results — of ballots received in the previous days — after 8 p.m. on election night. Many counties do daily updates after that, but because of the number of steps involved in ballot verification, including sorting, signature verification and assessment of ballots for extraneous marks, the updates can feel painfully slow.
In California voters also have the option of balloting by mail. Those ballots too must be postmarked by Election Day and received no later than three days later. In past elections, some close California races have not been called for days.
HOW MANY STATES VOTE BY MAIL?
According to the National Conference of State Legislatures, 37 states and the District of Columbia offer some type of early voting, and 27 states and D.C. offer "no-excuse" absentee voting. While more than 20 states allow certain elections to be held by mail, only Washington, Oregon and Colorado conduct all elections exclusively by mail.
Colorado and Oregon both require that ballots, whether they are mailed or dropped off, be received by elections officials no later than Election Day. In Washington state, ballots just need to be postmarked by Election Day.
WHAT DO SUPPORTERS OF VOTE-BY-MAIL SAY?
Former secretaries of state, Phil Keisling of Oregon and Sam Reed of Washington, co-wrote an op-ed in the New York Times in September lauding what they call "vote-at-home" laws that they credit for higher turnout in those states. More than 80 percent of voters in Oregon and Washington returned their ballots in the 2016 general election; the national turnout rate was about 61 percent.
"Vote-at-home's power derives from it being an opt-out rather than an opt-in election system," they wrote. "Election Day realities for other voters — bad weather or traffic jams, work schedules and family obligations — don't thwart our voters in exercising their most fundamental of rights."