We really need to take a step or two back to appreciate just how weird Trump's entire Ukraine gambit was. Not only was the type of scandal he was trying to gin up on Biden (tarring a candidate with corruption because of the foreign business conducted by his child) something that Trump himself is even more vulnerable to, but he went so far as to completely reshape the U.S.'s entire relationship with Ukraine just so he might be able to get a single line of attack against someone who is far from certain to be Trump's opponent.
Biden has a fairly good chance to win the nomination, but I would give it less than 50% (I'd guestimate it is around the 30-40% range). Of course, I could easily be wrong and Trump might see it differently. Maybe Trump thinks Biden is the runaway favorite. But given how bad the President's instincts are about anyone other than his base, that is just another strike against Biden's chances.
