In a significant step toward President Barack Obama’s goal of enacting a major overhaul of health care this year, the Senate Finance Committee is set Tuesday to begin marking up an $856 billion reform package.Finance Chairman Max Baucus (D-Mont.) expressed hope last week that the markup could be completed by week’s end. But with 564 amendments filed, there is no assurance that the process will run smoothly.Finance Democrats met Thursday evening, before the Senate adjourned for the weekend, to discuss their strategy for this week’s markup. Finance Republicans also met last week to discuss how to approach the amendment process.Meanwhile, the Progressive Change Campaign Committee and Democracy for America announced they are spending $100,000 on a television ad aimed at pressuring moderate Sen. Olympia Snowe (R-Maine) to support Obama’s health care agenda. The spot is scheduled to run in Maine and in Washington, D.C. “Olympia Snowe is fundamentally out of step with her constituents if she opposes a public option,— Adam Green, co-founder of PCCC, said in a prepared statement.Snowe was one of three Democrats and three Republicans on the Finance Committee who spent months trying to negotiate a bipartisan health care reform bill. Baucus chose to move ahead with the markup absent a consensus, but has left open the possibility of an agreement materializing during the markup. Snowe has said she doesn’t support Baucus’ proposal as it currently stands, but hasn’t ruled out backing it down the road.The Finance bill includes a proposal for a nonprofit, medical cooperative, rather than the public insurance option — a clear bid to garner the support of Republicans and moderate Democrats opposed to the public insurance option. Liberal lawmakers prefer the public insurance option, and many have said they will not support any health care overhaul that lacks one.