President Trump last week floated the idea in a tweet that the presidential election should be postponed, after alleging that mail-in voting would mar the results. His tweet underscores what Joe Biden, the presumptive Democratic presidential nominee, alleged in the spring: The president and his allies could “indirectly steal the election” by alleging massive voter fraud if Biden and the Democrats win big.

How exactly would this work? In one scenario, even if Biden wins the popular vote in a state, a Republican governor or state secretary might refuse to certify the state’s slate of electoral college electors. That would mean that not enough electors would be selected, resulting in no presidential candidate being able to win a majority (270) of the 538 electoral college votes.

Under the Constitution’s 12th Amendment, such a move would throw the election to the House of Representatives — empowering the newly elected House in January to vote to select the president. But here’s the rub. The Constitution directs the House to vote by state delegation, and Republicans currently hold a majority of the House’s state delegations. Assuming that the GOP maintains that lead in the new Congress and that lawmakers would vote for their own party’s nominee, the House would thus elect a Republican as president. As former Colorado senator Timothy Wirth and Newsweek’s Tom Rogers put it, this is how Trump could “lose the election and still remain president.”

Democrats could retaliate if they were willing to play what’s called “constitutional hardball” — stepping outside democratic norms without technically violating the Constitution’s limits, as when Senate Majority Leader Mitch McConnell (R-Ky.) refused to convene a hearing to consider President Barack Obama’s Supreme Court nominee Merrick Garland. That’s something some observers claim Democrats are typically reluctant to do. But if Democrats were to play tough, here’s a constitutional curveball they could throw.

Here’s how the certification of electors usually works

The process for appointing electors to the electoral college is so routine that we hardly notice it. Federal law requires that “the executive” (usually the governor but sometimes the secretary of state or other high official) communicates the state’s slate of electors to the national archivist. The archivist transmits those lists to Congress, which oversees electoral college voting.

While some electors have voted against the candidate that won their state’s majority, states have always reported their slate of electors. Even in 1800 and 1824, when the House decided the presidential election by what’s called the contingent vote procedure, all electors were reported to the electoral college. The scenario described above would be unprecedented — but not impossible.

Here’s how Democrats would be able to retaliate

Assuming the new House reelects Nancy Pelosi (D-Calif.) as speaker, Pelosi could use the chamber’s power under the Constitution’s Article I, Section 5, to have her majority be the “judge” of contested elections to the House. The House could then seat enough Democrats to give Democrats control of a majority of state delegations before the House votes to select the president in January 2020.

Here’s how this might play out. As the judge of contested elections, the House can entertain any challenge to the election results at the beginning of its session (after choosing the speaker, customarily its first vote). Usually, the House refers these challenges to a committee to investigate. The committee recommends awarding the seat to one or another candidate, and the House votes on that recommendation. If enough Democratic challengers surfaced to allow the Democrats to claim a majority of delegations, then the attempt to manipulate the presidential election could be reversed.

Recent contested elections have tended to avoid brazenly partisan outcomes. For instance, in 1996, a Republican Senate seated Democratic Sen. Mary Landrieu of Louisiana despite a challenge from her Republican opponent. But majority parties regularly padded their majorities in the 19th century using strategically contested elections. In other words, 19th-century parties would strategically challenge the minority party’s winners to disqualify them and to brazenly install their own supporters, often in the session’s first weeks or months.

Do two wrongs make a right?

The Constitution was not drafted with the expectation that the House would regularly elect the president; the Founders saw that as a fallback measure when there were too many candidates for any one to win a clear majority of electors. A critic might argue that having the House decide the election should be done only if state officials first act in an undemocratic way, defying the “republican principle” that in a fair election, the majority vote is treated as the voice of the people.

The 12th Amendment’s mechanism for throwing an election to the House was used just once: In 1824, the House voted by delegation to elect John Quincy Adams as president. In that case, all 261 of the electoral college voters showed up — but with votes divided among four candidates, no one came close to a clear majority of 131 votes.

That couldn’t have happened had there been just two parties and two candidates, as we have today. In 2020, if all electors show up, only a 269-269 tie would deliver an inconclusive electoral college vote. In such a situation, it would hardly seem democratic for the House speaker to play hardball to capture the presidency.

Just threatening constitutional retaliation could be enough

If Republican state officials were to suggest they might withhold slates from the electoral college in November or December, Pelosi could threaten to reconstitute the delegations under Article I, Section 5 to preserve a genuine Biden victory, should one exist — thus signaling that Democrats would meet hardball with hardball. The option, in other words, could be useful even if she never has to use it.

Because all this would be unprecedented, we don’t know exactly what would happen. If state officials didn’t report electors, would the courts force them to do so? They might. But they might not, given Chief Justice John G. Roberts Jr.’s preference for leaving issues that the court deems “political questions” to the states and other branches of government.

Daniel Carpenter is the Allie S. Freed professor of government at Harvard University and author of the forthcoming “Democracy by Petition: Popular Politics in Transformation, 1790-1870” (Harvard University Press).