It's Election Day. Control of Congress is on the line, and what else you need to know

📲 Get the latest on the midterms & more in the NPR AppVote counting starts tonight. Follow along as polls close — and tune in to our live special starting at 8 p.m. ET.• Hour-by-hour guide: How to watch election night• 6 things to watch for to see which party might control Congress• Be patient!

It's going to take a while to know who won in some races It's finally here. Today, voting officially ends. More than 54 million people have already cast ballots.

That's nearly half of the total ballots cast in the last midterm election. Democrats hold a double-digit advantage going into today, based on available data from early voting. But a major key today will be how many Republicans show up to the polls.

There are so many red states and districts in play, and the GOP votes overwhelmingly in person on Election Day. Democrats are favored to win the House. They only have to flip three seats for control, and the landscape has shifted considerably, even in the past month, in favor of Democrats.

Republicans tried to insulate themselves with rare, mid-decade redistricting. But it likely won't be enough to help the party keep the chamber. In the Senate, the outcome is anyone's guess.

Democrats need to flip four seats to gain control of the Senate, something that was unthinkable at the beginning of this cycle. But strong Democratic recruits and a difficult national political environment for Republicans have made it a possibility. Democrats are favored to flip one seat — North Carolina.