When President Barack Obama ran for re-election, Democrats made no secret of their disdain for Mitt Romney. That was all before Donald Trump.

Horrified by the prospect of Trump in the White House, Obama and his party have changed their tune about Romney. As they denounce Trump as “unhinged” and unfit, they’re getting nostalgic about the 2012 Republican nominee they now describe as principled, competent and honorable.

It’s a sharp reversal from four years ago. Back then, Democrats spent hundreds of millions of dollars portraying the former Massachusetts governor as a callous, unpatriotic, pet-abusing caricature of the uber-rich....

It’s this year’s great irony that the same Democratic attacks that landed hard on Romney seem to bounce right off of Trump. Where Romney had to downplay his wealth, Trump boasts of his riches, and brushes off controversies over remarks perceived as insensitive to women or minorities.