It’s not an ad hominem if I thoroughly attack your argument.
You’ve already been guilty of moving the goalposts. Now you’re claiming he wasn’t a front runner because he didn’t do well in a state who wouldn’t have their primary for another 7 months.
In July 2019, when Trump made his call, Biden was both a candidate for president and leading in the polls (both for a primary and a head to head matchup in a general election with Trump).
As I said, your excuse is idiotic. One would have to be a moron to believe it.