(The Hill) – In this year’s tighter-than-expected battle for congressional control, it may be days before Americans know whether President Biden’s Democrats hold the House of Representatives, or whether Republicans will clinch the majority.

Republicans’ rumored red wave failed to sweep over Election Day on Tuesday, and Democrats delivered surprising blue wins in key races. But the overall power balance in both the House and the Senate was still too close to call Wednesday. 

This year’s midterms marked a rare Election Day where the night wound down without a clear projection for which party will control Congress. Along with a tight race for the House, Democrats are still hoping the toss-up Senate race will lean in their favor.

There’s no definitive timeline for when calls for the remaining House races will roll in. Because the race for congressional power this year is precariously close, it may be days or even weeks before a final call can be made. 

Here are five things to know in the ongoing tally to determine control of the House:

Dozens of races haven’t been called yet

All 435 seats in the House of Representatives were on the midterm ballots, and a party needs 218 to take the majority power. 

The latest Wednesday projections show Democrats with 183 House seats and Republicans with 207 seats. There are 45 seats still to be called. 

For the most part, parties have already picked up most of the seats they were expected to easily win, with the exception of some likely blue seats on the West Coast that haven’t been called yet. 

Most of the races still up in the air are either narrowly projected for one party over the other or have been flagged by forecasters as highly competitive, making it harder for a clear winner to be called. 

Republicans are the favorite to win the majority

Rep. Lauren Boebert (R-Colo.)

Rep. Lauren Boebert (R-Colo.) leaves the Capitol following the last votes of the week on Friday, September 30, 2022. The House returns on Nov. 14 following the midterm elections.

Republicans are leading in 14 uncalled races nationwide — GOP wins in all those seats will push the party over the 218-seat threshold and win a thin majority.

But the small-margin forecast is far from the “red tsunami” sweep some pundits and members of the GOP predicted heading into Tuesday’s election, and Democrats were able to pull off a handful of surprising wins. 

In Rhode Island, Democrat Seth Magaziner was projected to win the 2nd Congressional District after recent polling showed his Republican opponent pulling ahead.

In Colorado, Democrat Adam Frisch appears to be pulling ahead of Republican Lauren Boebert in a district Republicans were expected to win easily. 

Heading into Election Day, Republicans needed to pick up just five more seats to take the House reins from Democrats. Current projections show they’ve grabbed 10 seats so far, and the party is still favored to win control of the lower chamber — but unexpectedly close races across the nation have added to the tense anticipation of the final outcomes.

Mail-in ballots prolong answers in some key races

In this July 1, 2020, file photo, a woman walks past a vote-by-mail drop box for the upcoming New Jersey primary election outside the Camden, N.J., Administration Building.

A chunk of the races still to be called are on the West coast, where polls were some of the last in the nation to close on Tuesday night. 

Washington, Oregon and California along the Pacific border all offer universal mail-in voting and accept ballots that are postmarked as late as Election Day — meaning that it may take days for votes to even arrive at election offices for tabulation, prolonging the count for closer races. 

The one Oregon district with a Republican in the lead is the 5th congressional district, where Republican Lori Chavez-DeRemer leads Democrat Jamie McLeod-Skinner by a mere three points, with just 69 percent of votes reported so far. 

Mail-in ballots are also prolonging results in Pennsylvania. The state’s acting secretary of state on Tuesday told voters it could take days to accurately count the state’s much-anticipated midterm ballots and asked for patience before final results could be released.

The West Coast could give Democrats a boost

With the U.S Capitol in the background, people walk down steps on Election Day in Washington, Tuesday, Nov. 8, 2022.

Historically blue California is home to 22 still-uncalled races, and the state could deliver a big blue boost when the counts come in. At this point, Republicans are leading in just seven of those uncalled races.

Democrats are expected to easily pick up around 10 seats from the state, which would put the party closer to its 218-seat goalpost. 

Democrats lead in two remaining Washington districts and two of three leftover districts in Oregon — meaning the three West Coast states alone could potentially deliver 20 more wins for Democrats. 

Further inland, blue candidates are also leading in the three remaining Nevada districts and two districts in each of Colorado and Arizona.

Close races could stretch out the timeline

Pennsylvania Democratic candidate for Senate John Fetterman and Republican candidate Dr. Mehmet Oz

Pennsylvania Republican candidate for Senate Dr. Mehmet Oz and Democratic candidate John Fetterman.

Democrats are generally more likely than Republicans to cast early ballots and vote by mail, while Republicans appear to prefer same-day, in-person voting — and state-by-state variations in the rules on whether early ballots can be counted before or after Election Day may lead to “mirages” in the early counting stages. 

In Pennsylvania, for example, some Democrats warned that Republicans may appear to lead in some key races as Election Day ballots were counted, while Democrats would surge in as mail-in ballots were tallied.

And tallying could take even longer in treacherously close races if it any recounts are necessitated or ordered.

A recount was ordered in the Pennsylvania Republican primary this year when candidates Mehmet Oz and David McCormick came in neck-and-neck. A GOP secretary of state candidate in Colorado paid a quarter-million dollar fee for a recount in the state despite a double-digit initial loss.