The Change to Win coalition of unions has decided to endorse Barack Obama for the Democratic presidential nomination, a move that will give the senator from Illinois another big boost at a point where his campaign seems to be going from strength to strength.

“Change to Win is excited to announce the endorsement of Barack Obama for President,” Change to Win chair Anna Burger said today. “We are the unions that organize and mobilize working people and believe that we can make a huge difference on the ground in the upcoming primaries. Change To Win is the new labor movement, the labor movement of the 21st century and we are excited about our ability to make a difference.”

Coming on the heels of endorsements of Obama’s candidacy in recent weeks by key players in the Change to Win coalition — the Service Employees International Union, UNITE HERE, the United Food and Commercial Workers International Union and the International Brotherhood of Teamsters — the endorsement essentially signals that Obama will have the labor support he needs in states with primaries scheduled for March and April, such as Ohio, Texas and Pennsylvania.

He will not, however, have all the labor support he wants.

Key unions, including the American Federation of State, County and Municipal Employees and the International Association of Machinists, are working hard for Hillary Clinton. Indeed, some of Clinton’s union backers are developing quite an edge, as anyone who heard Machinists union president Tom Buffenbarger introduce the New York senator at a recent Ohio rally knows.

Buffenbarger tore into Obama, referring to the senator as a “thespian,” and “the man in love with the microphone.” And he bluntly dismissed the movement that backs Obama as the antithesis of a working-people’s campaign. “Give me a break!” growled Buffenbarger in Youngstown. “I’ve got news for all the latte-drinking, Prius- driving, Birkenstock-wearing, trust-fund babies crowding in to hear him speak! This guy won’t last a round against the Republican attack machine. He’s a poet, not a fighter.”

The Change to Win coalition thinks differently, although it should be noted that the coalition is not reading precisely from the same page. One Change to Win union, the United Farm Workers, backs Clinton, a not inconsequential fact with voting coming in Texas, where the union has been an influential player in Latino politics. Additionally, the powerful Laborers’ International Union of North America abstained from the endorsement because it is in the midst of a membership survey on whether to back Obama or Clinton.

That said, the Change to Win endorsement is significant.

CTW refers to Obama as “the American Dream candidate,” and the coalition and its Obama-backing affiliates plan a major push on the senator’s behalf among union members in upcoming primary and caucus states.

Still in play? Two of the most important industrial unions in Ohio and Pennsylvania, the United Auto Workers and the United Steelworkers. Both were friendly to the John Edwards campaign. That’s another reason why Obama and Clinton continue to court not just particular unions but former candidate Edwards.