Dhaka, Nov. 5 -- Donald Trump asked Americans to treat the midterm elections as a verdict on his presidency. He repeated the invitation dozens of times, urging voters to imagine that his name was on the ballot. When the votes were counted, they had delivered a verdict -- just not the one he wanted.

The Democratic sweep, reaching beyond traditional battlegrounds into Republican strongholds, exposed the strains within the coalition that twice propelled Trump to the White House.

For a president who has made personal loyalty the defining currency of his party, the scale of the defeat was more than an electoral setback. It was a warning about the limits of his political command.

By early Wednesday, estimates put the Democratic lead in the H...