Harris still has work to do to win over older, white, working-class voters who make up a large portion of the electorate in the Rust Belt.

Teamsters General President Sean O'Brien said his union would decline to endorse a presidential candidate this year, setting off a wave of criticism and commentary.

For the first time in nearly three decades, the International Brotherhood of Teamsters won’t endorse a candidate in the presidential race — a blow to the Democratic Party, which has reliably received the union’s approval for years.