Senate Republicans are pledging to block any Supreme Court nomination by President Barack Obama until after November, hoping a Republican will replace him and fill the vacancy left by Justice Antonin Scalia.

But even if the Senate refuses to confirm Obama’s pick and a Republican wins the White House, there is one way Obama can still get his nominee confirmed.

It could all come down to 17 crucial days in January.

If Democrats win back the Senate and lose the White House in November, they would control both branches of government for about two weeks before Obama leaves office. That overlap in the transition of power is set in stone. TheConstitution mandates the new Congress begins work on January 3, while President Obama stays in power until January 20.

So if Democrats take back the Senate, President Obama could send a Supreme Court nominee to that new Democratic majority, which would have 17 days to change the filibuster rules and ram in a vote before a new President takes power.

Related: Inside the Knotty Fight to Replace Justice Antonin Scalia

“If a Democratic Senate comes in on January third, President Obama could send in his Supreme Court nomination,” explained a former Obama administration lawyer. “Then Democrats could apply the ‘nuclear option’ to Supreme Court nominations, and vote in Obama’s nominee by a simple majority.”

Senate Democrats already used the ‘nuclear option’ to eliminate filibusters for most judicial nominees in 2013, but exempted Supreme Court nominees from the change.

The provocative scenario for January 2017 is certainly not the White House’s first choice.

President Obama is currently calling on the Senate to hold a “timely” vote on the nominee he selects, while Republicans insist that request is dead on arrival.

The very prospect of Democrats muscling in an Obama appointee next year, however, could impact the wrangling between the parties this year.

Immediately after Justice Scalia’s death on Saturday, top Republicans openly said there is only upside to blocking any Obama nominee.

Their initial calculus — shared by many political analysts — is that this nomination standoff will turn on who wins the White House. Republicans only stand to improve their position, the thinking goes, by waiting to see if they win the presidency.

But the prospect of a January power play sets up a potential alternative outcome — where the Supreme Court vacancy actually turns on the result of the Senate races.

“The possibility shows Republicans could overplay their hand,” said the former Obama official, who requested anonymity to discuss a strategy which assumes Obama’s nominee won’t be confirmed this year.

“If Republicans act in a way that jeopardizes Senate seats,” the official argued, “then it doesn’t matter who wins the presidential election.”

In fact, if Republicans completely block a “consensus” Obama nominee all year and then lose the Senate, Obama might be tempted to appoint an even more liberal replacement for Scalia in January.

It would all depend on President Obama’s approach to his last major act in office, coupled with how far Senate Democrats are willing to go.

Related: Obama’s Election Year Supreme Court Choice is Not Unprecedented

The prospect of Obama departing with a super progressive nominee is not considered far-fetched in some conservative circles, where Obama’s use of executive power in his second term is seen as proof of strident, far-left impulses.

Asked about a scenario where Scalia’s seat remains open after the Senate and White House change hands, a former senior Republican Senate aide said, “I have no doubt about the fact that Democrats would complete the ‘nuke.’”

That view was offered as a criticism — that Democrats will continue to change the rules when it benefits their agenda. Senate Republican insiders have long argued that Democrats politicized the nomination process by filibustering George W. Bush’s judicial nominees when convenient, then stripping Republicans of that same power when Obama took office.

Democrats have historically countered that Republicans stalled for more nominees, while this week, Democrats have said Republican attempts to reject Obama’s nominee sight unseen presents a new low.

Is this hypothetical escalation likely to be tested in January?

It’s obviously too early to handicap a presidential race where no nominees have been picked. Election experts say the Senate may be a toss up, as Democrats only need to win four seats for a bare majority in January, while Republicans are defending far more seats (24 of the 34 up for election this cycle).

As for legislative precedent, no president in the modern era has pushed a high-profile nominee through during his last 17 days in office.

President Bill Clinton did resubmit several of his judicial nominees to the Senate during his 17-day window in 2001, arguing that the previous Senate had obstructed them for no good reason.

At that time, the newly elected Senate was stuck in an unusual 50-50 split. So it tipped to one party for its first 17 days, thanks to Vice President’s Gore’s tie-breaking vote, and then back to Republicans once the new administration was sworn in.

In an election year that has already brought many surprises, the balance of the Supreme Court could turn on the fate of four Senate races and those crucial 17 days in January 2017. SOURCE