Senate Finance Chairman Max Baucus (D-Mont.) spent Monday working to build support among Democrats for his $856 billion health care reform bill, hoping to head into today’s markup having satisfied at least some of his colleagues’ concerns.

Finance Democrats met late Monday to resolve differences over Baucus’ proposal and strategize in of advance today’s markup. According to a Democratic source close to the discussions, Baucus plans to adjust his proposal to deal with several of the concerns raised by Members’ 564 amendments, most particularly on affordability.

“Baucus will be modifying his mark to bolster it based on the amendments filed Friday. Versions of Democratic and Republican amendments are included in the modification,— this Democratic source said. “We then expect robust debate for several days on important amendments, and expect amendments to be adopted as part of the markup.—

Both Democrats and Republicans on Finance expressed concerns about a provision that would require individuals to purchase health insurance — and the penalty owed to the federal government for not doing so. Additionally, there was a concern that the mandate might be too burdensome for lower- and middle-class families who are not poor enough to qualify for federal assistance.

Baucus’ most significant adjustments appear aimed at addressing these issues while still ensuring that his bill remains deficit-neutral. The Finance chairman is slated to unveil his modified mark today.

Senate Democratic sources say Baucus heard his fellow Finance Democrats loud and clear, and decided to adjust the bill to try to secure their support. Those sources said Democrats are warming to the proposal because they finally feel as if they have a say over the legislation.

Baucus spent several months negotiating with just five other Finance members, including three Republicans, in an attempt to reach a bipartisan deal on health care reform. A senior Democratic Senate aide said Baucus reached a “tipping point— with Finance Democrats when he introduced a bill they felt tilted right, but failed to garner any GOP support.

“This week will be a cathartic process. Democratic Senators not in the gang of six will finally get their chance to weigh in,— this aide said. “We’ll be able to say [at the end of the markup] that this bill is stronger than when it was received [today].—

Finance Democrats on Monday continued to negotiate how they would approach the markup, including whether to accept a key provision calling for a nonprofit medical cooperative rather than a public insurance option. Liberals prefer the public insurance option, while moderates tend to favor the co-op.

Finance Republicans, however, have already settled on their plan of attack.

The GOP amendments are likely to focus on stripping some of the fees and mandates Baucus’ bill would levy on individuals and portions of the health care industry, and on how the legislation would affect Medicare. Baucus has argued that his legislation would improve the program’s efficiency and root out waste, fraud and abuse; Republicans charge that the package would severely cut Medicare funding.

Republican Finance members plan to push for a rewrite of the bill, but they aren’t optimistic they will be successful.

“If my amendments were adopted, I could support the bill,— Senate Minority Whip Jon Kyl (R-Ariz.) said. “But I’m not holding my breath that the Democrats will be in such a wonderful, bipartisan mood that they would accept my amendments.—

As a Finance member and the No. 2 Senate Republican, Kyl is expected to figure prominently in this week’s markup. Finance Republicans met Thursday with Senate Minority Leader Mitch McConnell (R-Ky.) to map out their approach to the amendment process.

Republicans on the committee also are likely to take some cues from Finance ranking member Chuck Grassley (R-Iowa), and possibly Sen. Mike Enzi (R-Wyo.), who is also the ranking member of the Health, Education, Labor and Pensions Committee.

Grassley, Enzi and Sen. Olympia Snowe (Maine) were the three Republicans in the gang of six, along with Baucus and Democratic Sens. Jeff Bingaman (N.M.) and Kent Conrad (N.D.). Grassley and Enzi ultimately declined to support Baucus’ bill over several policy proposals and because they felt as if the Finance chairman rushed into the markup to satisfy the White House and Democratic leaders.

Snowe also has withheld her endorsement. But her support is still considered achievable; she is the only Republican on Finance who Democrats believe is in play.

“Kyl, as the Whip, holds sway,— a senior Republican Senate aide said. “Grassley is in the middle of that, too, because lots of folks are galvanized behind him on some issues.—