Unions that were either neutral or backing Hillary Clinton during the Democratic primaries are rapidly endorsing Barack Obama.

Among those announcing this week that they will back Obama are the United Auto Workers, the United Transportation Union, and the Sheet Metal Workers. Also signaling that their unions will endorse Obama are Ed McElroy, president of the American Federation of Teachers and Gerald McAntee, president of AFSCME.

The UAW endorsement of Obama, by a unanimous vote of its executive board on June 10, means that three large unions that have high percentages of male blue collar workers among their memberships are now backing the Illinois senator. The other two such unions are the Steel Workers and the Mine Workers.

The UAW was neutral during the primary contests. The Steel Workers and Mine Workers originally backed former Sen. John Edwards. After Edwards, who dropped out, endorsed Obama the two unions followed suit.

These latest endorsements bring the AFL-CIO closer to a federation-wide endorsement of Obama. To endorse the federation must have the votes of General Board members representing two-thirds of the 9 million members. Official backing for Obama must come first from several pro-Clinton unions including AFSCME, the American Federation of Teachers and the International Association of Machinists.

Thomas Buffenbarger, president of the Machinists and a superdelegate to the Democratic National Convention, is now “undecided.” He had been a strong Clinton backer.

McElroy has indicated that the AFT will engage in talks with its members. He did not indicate, however, that the AFT would move to endorse Obama before its July 11 -14 convention in Chicago.

McEntee said, “For our union, this election is about rebuilding America’s middle class. We look forward to talking with Obama and his staff about many of the issues our members care most about, such as ending privatization, providing state and local fiscal relief, fully finding and supporting public services and the workers who provide them, and guaranteeing everyone has quality, affordable health care they can count on.

“From the beginning of this campaign, our number one priority has been to take back the White House for America’s working families. During the primary season we showed that when this union makes an endorsement, we back it up with everything we’ve got, and that’s exactly what we are going to do in November,” McEntee declared.