Bernie Sanders just got a considerable boost from the "neither snow nor rain nor heat nor gloom of night" set.

The American Postal Workers Union Thursday announced on Thursday that it had endorsed the Vermont senator's run for the 2016 Democratic presidential nomination, giving him a solid vote of confidence as he races rival frontrunner Hillary Clinton to capture the support of major labor unions ahead of the primaries.

The APWU, which represents more than 200,000 postal workers across the country, said it was stirred by a "rousing" speech that Sanders delivered at the union's All-Craft Conference in Las Vegas late last month. In a statement heralding its endorsement, which comes just two days ahead of the second Democratic primary debate, the union praised Sanders's record, including efforts to save the postal service from privatization, as well as his "deep understanding" of the issues facing postal workers.

"Politics as usual has not worked. It's time for a political revolution," said APWU President Mark Dimondstein. "We should judge candidates not by their political party, not by what they say, not by what we think they stand for, but by what they do."

Sanders "doesn't just talk the talk. He walks the walk," he added. "He is a leader in the fight to protect the public Postal Service."

Dimondstein highlighted the senator's efforts to pass a "sense of the Senate" resolution this year to restore lowered service standards, and his support of "enhanced postal services, including postal banking."

"Based on his Senate record, we are confident he will appoint good people to public office and end conflicts of interest," he said. "He has already blocked the slate of nominees to the postal Board of Governors that includes the 'king of postal privatizers' James Miller and payday lending industry lobbyist Mickey Barnett. No other candidate has his record of exposing the rule of the billionaire class."

The APWU is the second major union to back Sanders at the national level. The 185,000 member-strong National Nurses United union endorsed the senator in August.

Clinton can boast of her own successes on the organized labor front, having secured the support of the American Federation of Teachers, which has more than 1.5 million members; the American Federation of State, County, and Municipal Employees, the largest public employees union in America, with 1.6 members; and various other unions, including those representing plumbers and welders, bricklayers, and aerospace workers.

While Clinton has cornered more trade union support, the recent endorsements for Sanders show that his effort to challenge the frontrunner from the left on labor issues is gaining traction.

Dimondstein capped off the APWU's endorsement Thursday by saying that Sanders not only stood behind postal employees, but all workers.

"No other candidate has his record of standing with workers on picket lines, fighting for a $15 per hour minimum wage," he said.