The Volokh Conspiracy
Mostly law professors | Sometimes contrarian | Often libertarian | Always independent
Those arguments make sense to me, but there's also a practical problem involved. An attempt at self-pardon might also be self-defeating: it might encourage precisely the federal prosecution it's intended to prevent.
Winning candidates usually don't try to jail the losers. That's for good reason: you want the incumbents to leave office peacefully, and you want the challengers to seek office peacefully.
Many people objected to the chant of "Lock Her Up" in 2016. It wasn't because—or wasn't just because—they believed Secretary Clinton to be factually innocent of any infraction of federal law whatsoever. It was also because a world in which elections determine who goes to prison is a world in which you can expect even more electoral mischief than we might see today.
Prosecuting former presidents is, in general, a bad precedent to set. That's one reason why it's important to deny the office to those whose conduct might force the issue. Whatever its virtues, the system of criminal law enforcement is not that great at handling crimes by those in high office. There's a good deal of discretion and rough-justice inherent in the system, and when high officers are in the crosshairs, that can reallocate political power to the wrong people. (Cf. why J. Edgar Hoover was bad.)
Normally, the real checks on presidential lawbreaking aren't criminal prosecutions and prison sentences. Rather, a presidential lawbreaker will face election losses, damage to their political party, and the undermining of a broader policy agenda. (Which is another reason why it's important to deny the office to those who are relatively indifferent to such things.)
An attempted self-pardon, though, threatens to set precedent in the other direction. If future Presidents think they can get away with it, they might try all sorts of unusual things while in office, secure in their ability to self-pardon before they leave.
So, if President Trump claims to issue himself a pardon, the Department of Justice in a Biden Administration might see the balance as pointing the other way. They might see it as crucial to restore a consensus that such pardons are invalid. And the only effective way to do that, once a President has challenged the consensus publicly, would be to bring such a prosecution and to have the pardon tested in court.
In other words, an attempt by President Trump to grant a pardon to himself could well result in the very prosecution that the Biden DoJ might otherwise forgo.
(It's yet another way in which the current administration can be both a symptom of the decay of crucial norms of behavior, and a cause of further such decay.)