[Reno89519]

Harris can recommend one, but both house and Senate need to approve, we have a rich history of leaving the position vacant, making speaker number two in line. My guess is that will be the result if Biden resigns.

[Track9]

I guess that would mean losing a tie braking vote in the Senate.

[Verginius Rufus]

We had long periods with no Vice President either because the President died in office (in some cases like William Henry Harrison, Lincoln, Garfield, McKinley, and FDR, very early in the term), or because the Vice President died in office. It wasn't until 1967 that there was a mechanism to fill the Vice Presidency if it became vacant.

Calhoun resigned the Vice Presidency but near the end of his term.