Inside the Decision Desk: When will we know Senate and House control?

In 2024, Donald Trump’s election night wins in the presidential battlegrounds of Georgia, North Carolina, Texas and Florida meant that most Americans went to bed on Tuesday with a good idea of the result of the election — and woke up to the networks having called enough states to declare Trump the president-elect.

Two years later, control of Congress is at stake. Republicans are trying to hang on to slim majorities in both chambers as Democrats try to wrest power in Washington for the final two years of Trump’s term.

Democrats are heavily favored in public polling in the House and in a number of key Senate contests — and if those numbers prove accurate, it’s possible that NBC News could project control of both chambers on election night. But it’s more likely that determining the winners in important races will take time.

Of course, no one, including the Decision Desk, will know what will unfold until election night, but we will have a good sense possibly early in the night of how the contests are trending. The answer of when we could call control in both the House and Senate depends not only on how states count their votes, but on how close the races will be.

When we could know Senate control

Senate control will likely come down to the eight races that NBC News rates as either toss-ups (Alaska, Iowa, Kansas, Ohio, Texas) or lean Democratic (Maine, Michigan, New Hampshire).

Assuming that Democrats win the states NBC News currently rates as “Likely” Democratic (which includes flipping North Carolina’s Senate seat from red to blue, and keeping Georgia in their column), Democrats still need to win five of these eight contests.

Some of these states are quick to count their ballots, and others are perennially slow. If some of these Senate contests are as close as we expect, calling control of the Senate as a whole could take us into the early morning hours of Wednesday, regardless of who wins those individual races.

It is also a real possibility that Americans will wake up at a slightly more reasonable hour on Wednesday without a majority decided, even if we have a good sense of who will ultimately win. And if Senate control comes down to the outcome in Alaska, we’ll all be here awhile.

In that case, it will take a couple of weeks to know who won the majority thanks to the state’s ranked choice voting system. Past elections offer a useful guide to how quickly we expect to see votes counted in each of these states, even if the timing Tuesday night is not exact. Let’s look more closely at each of these categories — the fast-counting states, the slow-but-steady states, and the ranked choice wild cards.

The fast counters

Votes in Iowa, Kansas, Ohio and Texas were counted fairly quickly in 2024. We expect over 80% of the vote in those states to be counted by midnight Eastern time. If those historical patterns hold, there is a good chance that those Senate races will be called. And some of these calls may come in before midnight if there is some spread in the races as some recent polls suggest.

But Democrats must win five of these battleground Senate races to take a majority, which means that even if they win all four states here, NBC News would still not be able to project control of the Senate.

The steady counters

In two of the key battleground states, New Hampshire and Michigan, nearly all votes will be counted over the course of election night, but more steadily and slowly than the fast counters. Here, elections are administered by towns and municipalities, not by counties. This results in a more decentralized and variable counting process that lasts until early morning, or even midday Wednesday. How quickly these races are called really depends upon the margin of the race.

Earlier in the election cycle, polls suggested both these races would be close. Recent polls favoring the Democratic candidates and what appears to be a Democratic advantage in the early vote in Michigan mean there’s a wide range of timing possibilities there.

If the nationwide Democratic momentum translates to results, New Hampshire could possibly be called before midnight. But that seems to be highly unlikely in a place like Michigan, where Wayne County, home to Detroit, often releases large batches of votes between midnight and 3 a.m. ET. This is such a significant source of ballots that statewide races in Michigan often cannot be called without Wayne County’s results.

The takeaway here is that if the Senate races in these states are close as the polls have indicated all along, it’s unlikely that calls will come before the early morning hours. But it all depends upon how far apart the two candidates are in the state, and we won’t know that until tonight.

The ranked choice states

Maine and Alaska are the slowest counters of the group. As in New Hampshire, Maine’s elections are administered by towns, each with their own schedule for tabulating ballots and releasing results. In Alaska, mail ballots from remote corners of the state can arrive up to 15 days after the election. If these historical patterns hold, there will not be enough votes counted on election night to call a close race in either state.

In 2024, the presidential race in Maine was called on Wednesday at 4:40 p.m. ET, and in Alaska on Thursday at 10 a.m. ET. Then-Vice President Kamala Harris won Maine by about 7 points, while Trump won Alaska by 13 points. It’s possible the margins in this year’s Senate contests could be much closer.

There is a second complication in Maine and Alaska that could cause even more delay in knowing which party will control the Senate. These states both use ranked choice voting for their Senate races, in which voters rank the candidates in order of preference. If no candidate is the first choice of more than 50% of voters, the winner will be determined by ranked choice tabulation, in which the candidate with the fewest votes is eliminated and their votes are reallocated based on voters’ next-most preferred candidates.

In Alaska, the ranked choice tabulation occurs 15 days after Election Day. Maine does not provide official guidelines on when its ranked choice tabulation will occur, but in June, the ranked choice results were released 10 days after Maine’s primary election.

In either case, if one or both of these seats are needed to win a majority, we may not know until the next day, or even for several weeks, which party will control the Senate.

What about the House?

Democrats only need a net gain of three seats to flip control of the House, and they’re heavily favored to succeed. But the size of that majority depends on how much voters shift their support toward the Democrats and away from Republicans.

A recent NBC News Decision Desk analysis shows evidence that this nationwide shift could be big enough to produce a historically large majority for the Democrats — or it could be sufficiently small that either party could end up with a razor-thin majority. (The House is made up of 435 seats, all up for re-election every two years, and 218 seats are needed for control.)

The size of that majority for either party matters significantly to our ability to project control of the chamber. The smaller the final size of the majority, the longer it will take for the Decision Desk to be certain of who will control the House.

If current polls are overestimating Democratic support and the size of the House majority for either party is small, the 2022 and 2024 elections provide some idea of timing.

During the 2022 midterms, it took the NBC News Decision Desk eight days after Election Day to project that Republicans would win a slim majority. This call came as the Decision Desk projected the Republicans would win California’s 27th District, their 218th win. The ultimate size of their majority was nine seats.

In the 2024 election, the Republicans won an even smaller majority — just five seats. This election also took until the second Wednesday after Election Day for the Decision Desk to project the 218th seat for the Republicans.

If the size of the Democrats’ or Republicans’ majority this year is a single-digit number of seats, we expect it to take days or weeks for either party to reach 218 seats.

Just like the Senate elections, the House elections in Maine and Alaska use ranked choice voting to determine a winner. If control of the House hinges on Maine’s 2nd District or Alaska’s lone district, we may have to wait until ranked choice tabulation occurs 10 to 15 days after Election Day.

On the other hand, if current polls end up being close to accurate, Democrats would be poised to win at least 230 seats, according to the recent Decision Desk analysis. This could speed up when we know control.

Throughout the night, the NBC News Decision Desk uses a statistical model to estimate the total number of seats that the Democrats and Republicans will end up winning. It is possible that NBC News will report this estimate on election night. The House model relies on past and current vote counts; it does not use any polling, including exit polls, in its estimation.

Early House indicators with clues for timing

Elections in states with early polling close times or that count their ballots quickly can also provide an indication of where things may end up. Kentucky’s 6th District, which Trump won in 2024 by 15 points, is a good example of an early bellwether district. The Republican-held district has its polls close at 6 p.m. ET, and in 2024 it reported nearly 90% of its votes by 8:40 p.m.

While the Democrats do not need their candidate, Zach Dembo, to win this district to earn a majority, a low-single-digit win by the Republican candidate, Ralph Alvarado, is a favorable signal for the Democrats’ chances of winning the House. If Dembo were to win this district, it would likely foretell a Democratic tsunami, as there are 267 districts nationwide where Trump performed more poorly on his way to the White House. And if Alvarado were to win by a margin close to or in the double digits, it may suggest that neither party will end up with a large majority.

Florida, which tends to report its votes quickly, also has several congressional districts worth paying attention to early in the night. One of these is Florida’s 25th, where Democrat Jared Moskowitz seeks re-election in a district that Florida Republicans redrew to favor Trump by 9 points. If Moskowitz loses to Republican Scott Singer, it would be a major victory for Republicans and may foreshadow the party holding on to House control. If Moskowitz wins comfortably, it may signal a large Democratic wave.

Florida’s 14th District and Florida’s 22nd District are also Democratic-held toss-ups that Republicans redrew to be districts Trump would have won by 10.5 points. Given how quickly Florida counts its ballots, these two districts may be the first toss-ups NBC News can project. If one party were to win both of these districts early in the night, that party could very well end up with the majority.