The Communications Workers of America (search) decided Friday to back Democratic front-runner John Kerry for president, giving the Massachusetts senator his second union endorsement.

The union's executive board voted in favor of the endorsement in a Friday morning conference call.

"Through the ups and downs of this very competitive race for the nomination, John Kerry has shown the toughness and tenacity that are needed to wage a successful campaign for the White House," CWA President Morton Bahr (search) said in a statement issued after the vote.

CWA is the nation's largest communications and media union, representing more than 700,000 workers in telecommunications, broadcasting, cable TV, publishing and electronics. It also has members in the airlines and health care industries.

CWA is one of a handful of major unions that has remained on the sidelines of the rollercoaster race for the Democratic nomination, because officials were uncertain which Democrat would emerge as a favorite that their members could wholeheartedly support.

For awhile, that Democrat looked like Howard Dean, the former Vermont governor who nabbed the top labor prize — support from the two largest unions in the AFL-CIO, the American Federation of State, County and Municipal Employees (search) and the Service Employees International Union (search).

Those two unions took a very serious look at Kerry in the fall, but went to Dean after campaign problems knocked off the Massachusetts senator as the preprimary front-runner.

Nearly two dozen industrial unions came out early for Rep. Dick Gephardt, who dropped out after his fourth-place finish in the Iowa caucuses. Dean also has stumbled, with Kerry winning both Iowa and New Hampshire.

Meanwhile, Michigan's largest teachers union on Friday threw its support behind Kerry. The Michigan Education Association endorsement came from one of the state's biggest unions, with 157,000 members. MEA President Lu Battaglieri gave the senator from Massachusetts his personal endorsement last July and has been working on Kerry's campaign, but the union stayed out of the race until now.

CWA's strategy to hold its fire appears to have paid off. It joins Kerry's sole union supporter, the International Association of Fire Fighters. Another union, the International Association of Sheet Metal Workers, is to announce its endorsement of Kerry in coming days.

"It is becoming increasingly clear that Senator Kerry is the strongest candidate to carry the party's banner and reclaim the White House from an administration that listens solely to the corporate and wealthy elites at the expense of working families," Bahr said.

Kerry has been a longtime friend of CWA, regularly speaking at the union's conventions and meetings and supporting legislation it favors. Just this month, Kerry introduced the "Call Center Consumer's Right to Know Act," which would require U.S. corporations' call centers to disclose their location to callers. The bill is intended to highlight the millions of call center jobs that have been outsourced to such countries as India, Brazil, Ireland and the Czech Republic.