As the Democratic Party convulses over questions about President Joe Biden’s mental fitness, a pair of well-connected Democrats is offering an optimistic plan that would involve the president stepping down as the nominee and the party announcing a “blitz primary” process ahead of the August convention. The proposal is the work of Rosa Brooks, a Georgetown University law professor who served in the Obama and Clinton administrations and as a volunteer policy adviser to the Biden campaign in 2020, and Ted Dintersmith, a venture capitalist and education philanthropist who has donated to various Democratic campaigns. They want Biden to flip...