The argument against Donald Trump from many of his rivals in the Republican nominating contest is that the former president will lose in the general election and drag his party down with him.

But the most effective argument in favor of renominating President Joe Biden on the Democratic side is that no one other than Biden can be relied upon to beat Trump.

The two arguments are in direct tension and will need to be resolved in the minds of the two electorates in the coming months. 

If Biden is so weak that among the GOP candidates, only Trump could lose to him, Republican voters will feel freer to take a chance on a lesser-known candidate. This is how Trump’s emphasis on corruption and his martyrdom serves his own electability argument. The system is so rigged that only I can survive it …