What Happens if the Vice President Steps Down?

There has been a strange rumor that Vice-President Harris may resign. I have no reason to credit the rumor; but it does raise a rarely-discussed question (which a reader e-mailed me about): What happens when a Vice-President resigns or dies or is impeached, or for that matter leaves office to become President and in particular what happens when there’s a 50-50 senate?

via reason.com

Not going to happen but still worth asking.