As a conservative watching the Democratic debates, I found that one of the most astonishing aspects of the multicandidate assault on Joe Biden was that the case against him seems to be based in large measure on his role in two generations of Democratic victories. His “crimes” consist partly in playing crucial roles in the political successes of two previous Democratic presidents — men who were personally so popular that it’s entirely likely that they would have won a theoretical third term.

In key issue after key issue, Mr. Biden isn’t running against the failures of the past. He’s running against the arrogance of the present.

Let’s take, for example, his role in passing Bill Clinton’s signature anti-crime legislation, the Violent Crime Control and Law Enforcement Act of 1994. Yes, it was tough on crime. It enhanced penalties; it expanded the death penalty; and it funded new police officers and new prison cells. It also included the Violence Against Women Act and an assault weapons ban that wouldn’t have a ghost of a chance of passing Congress today. Moreover, it did not play a material role in mass incarceration, which is a product mainly of state prosecutions, not federal law enforcement.

And what two additional elements do Mr. Biden’s critics miss? First, it was passed with overwhelming Democratic support (including a majority of the Congressional Black Caucus), which means that most of his present critics — had they been in office at the time — would have also voted for the bill.