AFL-CIO chief Richard Trumka, once a vocal critic of President Obama who even threatened to withhold support for his reelection, says passage of the adminsitration’s jobs bill should now be the “first task” of progressive and labor movements in the U.S.

“Like many of you in this room, I’ve been one of the first to call out President Obama when I thought it was needed. But when he’s doing the right thing, when he’s doing the courageous thing, it’s time for us to have his back and push that bill through and put people back to work,” Trumka told a cheering crowd at a Washington conference.

The comments are a sign Obama’s populist shift over the past few weeks has begun to win over members of his liberal base. Some have signaled that the American Jobs Act is becoming an effective rallying point for the 2012 campaign.

“When we call for fair taxes on those who fed on America’s economic collapse, they’ll cry ‘class warfare.’ But I’ll tell you, it wasn’t our class that declared war on working people and people who work for a living,” said Trumka. “If they want to have a debate on class warfare, bring it on down, we’ll have that debate.”