The senators sit on the Senate Finance Committee, which attempting to draft bipartisan health care reform legislation.

The Sheet Metal Workers union has purchased radio advertising targeting Republican and Democratic senators urging them to support a broad overhaul of the nation’s health care system.

The ads, titled “Which Side are They On?,” are airing in the districts of Sens. Chuck Grassley (R-Iowa), Kent Conrad (D-N.D.), Blanche Lincoln  (D-Ark.) and Max Baucus (D-Mont.).

The senators sit on the Senate Finance Committee, which attempting to draft bipartisan health care reform legislation.

"Access to health care coverage is a major problem facing millions of American families. That's why we support a strong public option, an employer mandate and no tax on health care benefits," said Michael J. Sullivan, the union’s general president. “It is imperative that these senators serve the American people and not an industry which has thrown millions of Americans into debt and ruin while reaping a 400 percent surge in profits over the last 10 years."

Remaking the nation’s health care industry and proving coverage to most of the estimated 45 million Americans who lack insurance is one of the top domestic policy goals of President Barack Obama. However, deep disagreements among Democrats on what the reforms should be and how expanded coverage should be paid for, combined with near-unanimous Republican opposition to current bills, has made winning passage difficult.

Baucus, the Senate committee's chairman, has said he hopes to vote to send a bill to the floor by mid-September.

The president has said he wants to sign a bill into law by the end of the year.