The decision as to who becomes president rests with those who operate under the Big White Dome on Capitol Hill.

The following explains what happens in Congress over the next few months as it goes about certifying the next president.

The Constitution makes Congress the ultimate arbiter determining which candidate wins each state. Congress must approve certificates of election from all 50 states. You may have thought November 3rd was the most important date on the election calendar. But a more crucial date is December 14, dictated by an obscure, Byzantine, 1887 law: The Electoral Count Act.

BIDEN WINS PRESIDENCY, TRUMP DENIED SECOND TERM IN WHITE HOUSE, FOX NEWS PROJECTS

Congress passed the legislation after the disputed 1876 presidential election between President Rutherford B. Hayes and Samuel Tilden. Electoral votes were unresolved in Florida, South Carolina and Louisiana -- where each party declared victory -- as well as Oregon, where an elector was declared illegal.

There was a sprint to settle the electoral college tally before Inauguration Day, 1877. Congress created an “electoral commission” to resolve the issues. In those days, the president assumed office on March 4.

The Electoral Count Act dictates that states choose electors no more than 41 days after the election. This is partly why the Supreme Court rushed to complete Bush v. Gore on December 12, 2000. The decision halted the count of ballots in Florida, handing the presidency to George W. Bush over the then-Vice President Al Gore.

The 1887 law establishes a “safe harbor” date so states conclude vote counts and establish electors early. But what happens if there are problems with the mail? The cryptic nature of the statute could give some states the green light to continue counting – or cease counting.

So what happens if a state sends inconsistent slates of electoral votes to Congress? The new, 117th Congress must hammer all of that out, starting on January 6, 2021.

Electoral vote “certificates” start filtering into the Capitol in December from the various states. This is in preparation for the House and Senate to meet in a joint session of Congress on January 6 to formally sign off on the results. 

MICHIGAN GOV. WHITMER CONGRATULATES BIDEN, PLEDGES TO BEAT 'COMMON ENEMY' COVID-19

Presuming House Speaker Nancy Pelosi, D-Calif.,  is re-elected to her leadership role, she and Vice President Mike Pence, in his capacity as President of the Senate, would co-preside over the joint session. Pence’s term doesn’t expire until January 20. And, the 12th Amendment to the Constitution mandates that “the President of the Senate shall, in the presence of the Senate and House of Representatives, open all the certificates and the votes shall be counted.” 

That phrase is key. It has vexed Constitutional scholars for decades. The 12th Amendment doesn’t dictate “how” the votes are counted. That’s why this could get dicey.

The 12th Amendment also says “the person having the greatest number of votes for President shall be President.” But Congress must agree to all of this. And remember, Pence is the one running the show at this stage.

Do not underestimate the role of the vice president at this critical stage.

Hawaii wasn’t a determinative state in the 1960 presidential election between then-Senator John F. Kennedy and then-Vice President Richard Nixon. Kennedy was going to win the White House, regardless of Hawaii.

Initial results from Hawaii showed that Nixon captured the Aloha State. But a recount shifted the win to Kennedy. Hawaii sent two slates of electoral votes to Washington: one for Nixon and one for Kennedy, both signed by the governor.

WHAT HAPPENS TO KAMALA HARRIS' SENATE SEAT NOW?

Going "by the book," Hawaii’s electoral votes should have gone to Nixon. But when the joint session of Congress convened in January of 1961 Congress handed Hawaii’s then three electoral votes to Kennedy. Nixon, the sitting vice president, presided.

But what would have happened had Nixon intervened, potentially, as the GOP presidential nominee who lost to Kennedy?

We’ll never know.

From a technical standpoint, once the House and Senate settle the Electoral College, that’s when the president-elect is on a glide path to the Oval Office. 

After the 2000 Florida election dispute, a cavalcade of Congressional Black Caucus members paraded through the well of the House chamber to contest the outcome in January 2001. Vanquished Democratic nominee, Vice President Al Gore -- like Nixon -- presided over the joint session as president of the Senate. 

“Mr. Vice President, I rise to object to the fraudulent 24 Florida electoral votes,” declared Rep. Maxine Waters, D-Calif. 

“Is the objection in writing and signed by a member of the House and a senator?” inquired Gore.

Congressional rules require a House member and senator to simultaneously challenge a state’s electoral slate. But Waters lacked a Senate sponsor.

“The objection is in writing!” snapped Waters. “And I don’t care!”

Gore, stood firm, despite having the most to benefit from Waters’ entreaty. 

“The chair will advise that the rules do care,” Gore intoned, triggering applause throughout the House chamber.

Questions arose in January of  2005 about Ohio’s slate of electoral votes. In that instance, the late Rep. Stephanie Tubbs Jones, D-Ohio and former Sen. Barbara Boxer, D-Calif., teamed up to challenge Ohio’s electoral votes.

The House and Senate then met separately to consider Ohio’s slate. But after a short debate, Congress decided that President George W. Bush was victorious in Ohio.

The Constitution does not mandate what the House and Senate must do to establish whether it “certifies” an electoral slate. And if the House and Senate actually debate or even vote on a disputed slate of electors from a state, what happens if each body reaches a different conclusion? It’s mathematically possible the presidential candidates fall shy of the required 270 votes to assume the presidency?

OBAMA CONGRATULATES BIDEN AND HARRIS: 'COULDN'T BE PROUDER'

It’s also unclear how fast all of this must happen.

Now we enter murky, Constitutional waters.

What happens if Congress hits an impasse when certifying the electoral college? First, there’s no game clock dictating that Congress has exhausted all options. But if Congress determines there’s a stalemate, the 12th Amendment directs the House to elect the president.

This is called a “contingent election.” The House has chosen two presidents via contingent elections: Thomas Jefferson in 1801 and John Quincy Adams in 1825.

Each state casts one ballot as a House delegation during a contingent election. The House only considers the top three electoral college vote-getters in a contingent election. Likely President Trump, Biden and, perhaps someone else. There have been 165 “faithless electors” in U.S. history. These are persons who vote for someone besides the candidates for whom they are pledged.

Faithless electors in 2016 directed electoral votes to former Secretary of State Colin Powell, former GOP presidential candidate and Ohio Gov. John Kasich, former Republican Rep. Ron Paul of Texas, Sen. Bernie Sanders, I-Vt. and Faith Spotted Eagle.

So, one vote per state in a contingent election in the House

Republicans currently control 26 state delegations. Democrats control 22. Two states are essentially tied. The GOP holds more state delegations than Democrats. But this is all decided in the new Congress. Moreover, dozens of House seats still aren’t settled yet.

But here’s the problem for Democrats: California has 53 House seats. However, California only counts as a solitary vote in a contingent election. By contrast, South Dakota has but one House seat. But, all states are equal in a contingent election. So, it’s possible that South Dakota or other small states would offset California’s presumptive delegation vote for Biden.

HILLARY CLINTON LAUDS BIDEN'S PROJECTED VICTORY AS 'REPUDIATION OF TRUMP'

The House wing of the Capitol wasn’t complete when its members met for the contingent election of 1801 between Jefferson, Aaron Burr and sitting President John Adams, the top three electoral vote-getters. So, House members huddled in what is now the office of Senate Majority Leader Mitch McConnell, R-Ky, on the Senate side of the Capitol to choose the third U.S. president.

Contingent election haggling consumed six days. Members finally broke the logjam on the 36th ballot, propelling Jefferson to the Presidency.

Nothing is written in the Constitution as to how long Congress has to work out who is president in a contingent election.

But what happens if the House hasn’t picked a president by noon ET on January 20th? That’s the Constitutionally-mandated day and time to inaugurate a president. This is where the 20th Amendment and the Presidential Succession Act kicks in.

HOW BIDEN, MCCONNELL COULD FIND THEMSELVES IN FAMILIAR ROLE AS NEGOTIATING PARTNERS

If the House remains stymied at noon on January 20, there is no president nor vice president. The terms of President Trump and Vice President Pence expire. But there is a Speaker of the House, next in line to the presidency.

This is where Pelosi, by statute, becomes “Acting President.” Not President. But “Acting President.” Whatever that means.

If nothing is settled by January 20th, this could create what scholars refer to as the “two claims scenario.” That’s where two people say they are rightfully the president on that date.

The U.S. came close to “two claims” with Hayes and Tilden in 1877. A back-room Congressional deal ultimately awarded the presidency to Hayes, even staving off a Senate filibuster (!). Congress determined Hayes won the Electoral College 185-184. Tilden captured the popular vote by three points.

CLICK HERE FOR THE FOX NEWS APP

Detractors called the new President “Rutherfraud” B. Hayes.

But Congress has to settle this before noon et on January 20.