At least the presidential experts haven’t lost their minds, even if most of the rest of us have. Biden makes his debut in our rankings at No. 14, putting him in the top third of American presidents. Trump, meanwhile, maintains the position he held six years ago: dead last, trailing such historically calamitous chief executives as James Buchanan and Andrew Johnson. In that and other respects, Trump’s radical departure from political, institutional and legal norms has affected knowledgeable assessments not just of him but also of Biden and several other presidents. […] Biden’s most important achievements may be that he rescued the presidency from Trump, resumed a more traditional style of presidential leadership and is gearing up to keep the office out of his predecessor’s hands this fall. Trump’s position at the bottom of our rankings, meanwhile, puts him behind not only Buchanan and Johnson but also such lowlights as Franklin Pierce, Warren Harding and William Henry Harrison, who died a mere 31 days after taking office. Trump’s impact goes well beyond his own ranking and Biden’s. Every contemporary Democratic president has moved up in the ranks — Barack Obama (No. 7), Bill Clinton (No. 12) and even Jimmy Carter (No. 22). Yes, these presidents had great accomplishments such as expanding healthcare access and working to end conflict in the Middle East, and they have two Nobel Prizes among them. But given their shortcomings and failures, their rise seems to be less about reassessments of their administrations than it is…