For the past century, the agendas of the Democratic Party were predictable: They professed concern for working Americans and supported blue-collar unions.

Unemployment insurance, a 40-hour workweek, disability insurance and Social Security were their trademarks — achieved by growing government bureaucracies and continually raising taxes.

Still, many Democrats were socially conservative.

They deplored antisemitism.

Party officials had rejected their own segregationists to champion civil rights.

Presidents like Franklin D. Roosevelt, Harry Truman and John F. Kennedy all supported strong defense and military deterrence.

All that is now passé.

The only vestigial Democrat left in Congress is Pennsylvania Sen.…