Labor unions are applying every ounce of pressure they have to get the final votes on the health care bill, focusing particularly on members who have said they would oppose the measure.

Yesterday, the AFL-CIO sent a letter to Mike Arcuri (D-NY) telling him they would not be able to support him if he voted against the bill. And Dr. Les Roberts, who ran against Arcuri in the primary in 2006, has already been approached as a primary challenger by leaders of the Working Families Party.

Today, the AFL-CIO sent a similiar letter to Stephen Lynch (D-MA), who emerged as a prominent No vote earlier this week.

“Congressman, we will not be able to explain to the working women and men of our union why you voted against their interests,” reads a letter from AFL to Lynch, dated this morning. “We have stood together time and time again and you have made an enormous difference in the lives of our members. It takes courage to make history. We know that you have always had the courage to do the right thing – national health reform is the right thing for Massachusetts families.”

There’s already talk of a primary challenge for Lynch – Harmony Wu, an Obama organizer from Needham, is considering a run.

United Steelworkers are holding a sit-in at the Pittsburgh-area office of Jason Altmire, who announced his intention to vote No yesterday:

Dozens of local United Steelworkers (USW) members and retirees are sitting in the Aliquippa office of Pennsylvania Rep. Jason Altmire today to urge the Congressman to change his vote for health insurance reform.

The working men and women and retirees represent the voters in Altmire’s district and across the nation who desperately want and need health insurance reform to pass so that our economy can get back in track. Reform will cut costs, save jobs, help our seniors and provide coverage for tens of millions of uninsured – may of them hard-working folks who despite having jobs cannot afford insurance.

“We busted our humps working for Jason Altmire and many other politicians who time and time again promise us that they’ll work for us and working families across America. We are tired of the broken promises. We helped Congressman Altmire win this seat because he vowed he would vote for health insurance reform. We’re here today urging him to keep that promise,” said Rick Galiano, president of USW Local 9305 in Beaver Falls, Pa.

The AFL-CIO and other labor unions are not the only ones talking about betrayal and primaries – Michael Moore has an open letter excoriating Bart Stupak for his hijacking of the health care debate, and endorses his primary challenger, Connie Saltonstall.