The death of US Supreme Court Justice Ruth Bader Ginsburg has handed President Donald Trump an opportunity to install a 6-3 conservative majority on America's highest court.
From her deathbed, Justice Ginsburg told her granddaughter: "My most fervent wish is that I will not be replaced until a new president is installed".
With only six weeks to go before the election, Mr Trump and his Republican allies have made clear they are not willing to wait.
During an interview on Fox News, President Trump even suggested Ruth Bader Ginsburg's final statement may have been written for her by senior Democrats Adam Schiff and Nancy Pelosi.
"I don't know that she said that, or was that written out by Adam Schiff or Pelosi?" he said.
"That came out of the wind. That sounds so beautiful, but that sounds like a Schumer deal, or maybe Pelosi or for Shifty Schiff. Maybe she did, and maybe she didn't."
The President said he would announce his nominee this weekend, after memorial services for Justice Ginsburg have completed.
Donald Trump says he would prefer to get the seat filled before the election. But even if he lost, he would still have a short window of time to push through a nominee in what's known as the 'lame duck session'.
The process could likely get ugly, but it can be done.
How does a judge get put on the bench?
When one of the nine seats on the US Supreme Court becomes vacant, the President gets to nominate a replacement.
There are no constitutional requirements for the age, experience, or citizenship of a Supreme Court justice.
The US Constitution only says that the President's nominee needs to be confirmed by the Senate.
For the last 70 years, that process has taken an average of 50 days, according to political website FiveThirtyEight.
With just 41 days to go before the election, Mr Trump and his Republican allies in the Senate have a small window to fill Ruth Bader Ginsburg's seat.
What happens next is up to the Senate Majority leader, Mitch McConnell.
Mitch McConnell holds the cards
About 90 minutes after Ruth Bader Ginsburg's death was announced, Senator McConnell promised a vote on Mr Trump's nominee.
Four years ago, he blocked president Barack Obama's nomination of Merrick Garland to the court on the grounds that it was an election year.
"Americans re-elected our majority in 2016 and expanded it in 2018 because we worked with President Trump and support his agenda, particularly his outstanding appointments to the federal judiciary," he wrote to explain his reversal this time around.
"Once again, we will keep our promise."
Supreme Court nominees are investigated by the Senate Judiciary Committee, before they attend a public hearing to discuss their legal background and positions on contentious issues like abortion access.
If Mitch McConnell wanted to rush through Mr Trump's pick, that traditional process could be condensed to just a few weeks or even days.
That option is not without risk.
The Republican majority in the Senate is slim — only 53 out of 100 seats are held by the conservative party.
Does he have the votes to replace RBG?
Several moderate Republicans have already said that Ruth Bader Ginsburg's dying wish that her seat remain vacant until after the election in November should be respected.
"For weeks, I have stated that I would not support taking up a potential Supreme Court vacancy this close to the election," Alaska senator Lisa Murkowski has said.
"Sadly, what was then a hypothetical is now our reality, but my position has not changed."
Susan Collins of Maine, who is at risk of losing her seat this November in a Democratic-leaning state, also says it would be better to wait until after the election.
"In fairness to the American people, who will either be re-electing the President or selecting a new one, the decision on a lifetime appointment to the Supreme Court should be made by the president who is elected on November 3rd," she said in a statement.
However, she has not said explicitly what she would do if Mr Trump pushed ahead with his nominee.
Chuck Grassley, Lindsay Graham and Mitt Romney are also being closed watched as Republicans who might break with the leader of their party, but they have been conspicuously silent since Ruth Bader Ginsburg's death was announced.
Four Republicans could sink Mr Trump's nominee if they decide they haven't been given enough time to examine their credentials.
If only three cross the floor, the Senate will be deadlocked. One man will be called upon to break the tie.
How Mike Pence could get to decide
Mr Trump's deputy Mike Pence is also the president of the Senate.
In the event of a 50-50 vote, the vice-president is allowed to cast the deciding ballot — and that is almost always in line with the ruling administration's party.
Mike Pence has not publicly stated what he would do, but his chief of staff Marc Short has dismissed Ruth Bader Ginsburg's request that her seat remain open until the November election.
"She's certainly a giant upon whose shoulders many will stand and she blazed a trail for many women in the legal profession," Mr Short said on CNN.
"But the decision of when to nominate does not lie with her."
What happens if they can't confirm a nominee before the election?
The Senate has never filled a Supreme Court vacancy this close to a presidential election.
If the Republicans lost the White House and the Senate on election day, they could still technically confirm a Supreme Court nominee in the lame duck session.
Mr Trump would remain President until Joe Biden took office on January 20, 2021. The US Senate doesn't adjourn until January 3.
They retain their powers to pass legislation and vote on presidential nominees before the new President and Senators are sworn in.
One Republican Senator has already said he would be happy to vote for President Trump's nominee even after he lost.
"You mean while we're still in our term office, and President Trump is? Of course," Senator John Cornyn told CNN.
But some Democrats say if a nominee were appointed in the lame duck session, they would immediately seek to expand the number of judges who sit on the Supreme Court.
Although the Supreme Court has consisted of nine justices since 1869, the constitution does not require that number.
A last-ditch attempt to cement conservative control of the court for a generation could see it dramatically transformed.