Well, the Trump team has been panicking in anticipation of this happening. They have already started launching law suits trying to stop it. The biggest scare they had was Biden's age and that may have just vaporised?
"President Biden put his country first and stepped aside. When Donald Trump was told by the voters to get lost, he called on his followers to march on the capitol."
OTOH, Biden countered a lot of their favourite lines of attack.
He was a white, catholic man who was obviously not rich. They couldn't attack his religious beliefs without inviting comparisons to Trump. They couldn't attack his race or his sex. They couldn't make him out to be a threat to American values, when his image was always very friendly and loving.
They're going to go hard on Kamala being the "DEI" candidate. They're going to go hard on her not being Christian (whether or not she is, they're going to imply that she isn't, just like they claimed that non-white Obama was a muslim). There are tons of lines of attack that are now open to them because they're not running against Biden anymore.
Nobody knows how this is going to turn out. It all depends on how undecided people vote. And, if you're undecided at this stage, you're an absolute moron. Who can predict the vote of the low-information moron voter?