IF it is obvious that Biden should step aside, who should take his place?

It seems it is more than just us here:

Dozens of Democratic lawmakers are considering signing a letter demanding President Joe Biden withdraw from the race, a senior party official said, as panic mounts that he’ll cost them control of Congress.

Biden is rapidly losing the support of Democratic lawmakers and candidates concerned the 81-year-old’s continued candidacy would lead to a Republican sweep of Washington and an unchecked Donald Trump presidency.