Political polarization contributed to unexpectedly close midterm election

Buoyed by economic problems and widespread dissatisfaction with the status quo, the party out of power expected to win big, only to underwhelm and even lose seats in one chamber of Congress.

That may turn out to be how this year’s elections end, depending on the outcome of the Georgia Senate runoff next month, but definitely describes the 2020 result — even if Republican gains in the House and competitiveness in battleground states that year were overshadowed by former President Donald Trump’s claims to be the rightful winner.

Trump, abortion, and questionable GOP candidate quality loom large as explanations for why the...