This is most apparent in the phenomenon that goes by the name of Donald Trump. Trump’s gratuitous insults of rivals reflect the coarseness of Obama’s nonstop insults of Republicans and anyone who does not share his views and priorities. Despite his pre-presidential promises of nonpartisanship, Obama has been the most grating and vitriolic partisan president of the last 60 years.

Trump’s more outlandish proposals — making Mexico pay for a border wall, making common cause with Russia in Syria — can be seen as a variation on Obama’s insistence that climate change is the nation’s No. 1 problem and his acquiescence in, well, making common cause with Russia in Syria.

And the adoring crowds that throng Trump’s monster rallies — what do they remind you of? The crowds that cheered Obama in 2008 as he promised to fundamentally transform America and stop the rise of seas.

The Republicans who have emerged as Trump;s chief rivals, Marco Rubio and Ted Cruz, had interesting beyond-the-Beltway careers pre-2008 (Rubio in the Florida legislature, Cruz in the Texas attorney general’s office) but emerged as national figures only after Obama’s inauguration.