As mourners hold nationwide vigils for Supreme Court Justice Ruth Bader Ginsburg, Republicans are planning for her successor.

"Now it says the president is supposed to fill the seat right? And that's what we're going to do, we're going to fill the seat," says President Donald Trump.

Trump says he expects to announce his pick for the Supreme Court by the end of the week - before Ginsburg is buried. Some say filling the seat could lead to a supreme fight.

"She said, 'My most fervent wish is that I will not be replaced by--until a new president is installed,'" says Sen. Chuck Schumer, (D-New York).

Some Senate Republicans argue it's their constitutional duty to fill the seat. Senate Majority Leader Mitch McConnell is pressing for a vote, but can likely only lose three GOP senators for the nomination to pass.

"Ordinarily I would say that this should wait until after the election, but this is unusual this year," says Rep. Pete King. "There are going to be so many states having their ballots contested in the presidential election, it will probably go to the Supreme Court and you can't have a court divided 4-4, we have to have a full complement of nine judges."

The feelings of having to choose a new justice right away is a reversal from four years ago, when the GOP-led Senate refused to hold a hearing or vote for Obama nominee Merrick Garland.

"He created a new rule, the McConnell rule. Absolutely no hearing, no vote, for a nominee in an election year. Period. No caveats," says Democratic presidential candidate Joe Biden.

But Republicans say this time is different.

"I think it can be expedited, listen, this is not the ideal situation, but these aren't ideal times," says King.