Fox News reports that the Teamsters union has decided not to endorse Hillary Clinton for president at this time. According to James Rosen, the union’s 26-member board decided unanimously to withhold endorsing Clinton.

Rosen’s Teamsters source cited three reasons. First, the Teamsters are unhappy with Clinton’s recent announcement that she opposes construction of the Keystone XL pipeline. Second, they want to see whether Joe Biden will enter the race.

Third, and most ominously for the Dems, the Teamsters reportedly want to talk to Republican candidates. They are particularly interested in Donald Trump, who has worked with unionized workers throughout his career.

The Teamsters have backed Republicans for the presidency in the past, and when they have, it’s been good news for the GOP. Richard Nixon, Ronald Reagan, and the first president Bush all received backing for the Teamsters.

The importance of the Teamsters’ endorsement is obvious. Political analyst Larry Sabato told Fox News, “You’re talking about well over a million unionized workers, a lot of them in key states.” The decision not to endorse Clinton now is “one more piece of evidence that [her] effort[s] to lock down the nomination have utterly failed,” Sabato added.

The Teamsters’ decision looks almost like an invitation to Biden to join the race. If the union were to support the vice president, it might well put him over the top, assuming a fairly close race.

Long-term, the Teamsters’ decision looks like evidence of a potential Democratic crackup. Slavish adherence to the demands of environmentalists, backed by the upscale, elitist wing of the party, seems destined to put the Dems at odds with the desires of the working class, the party’s traditional constituency.

David Frum sees another important fissure in the Democratic party — the division between minority groups pushing for a softer approach to crime and the desire of Americans for safe streets and homes. I’ll have more to say about this matter in an upcoming post.