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As Democratic fears increase that health insurance reform could slip away with a crucial vote for a new U.S. senator in Massachusetts, President Obama on Sunday used a church pulpit at a Martin Luther King Day service to say the massive health bill would be a victory for "decency."

Speaking to congregants at Vermont Avenue Baptist church in Washington, D.C., before heading north to rally for Attorney General Martha Coakley, Obama said the legislation will help more than 30 million Americans, "men women and children, mothers and fathers" to get insurance.

"This will be a victory not for Democrats," Obama said. "It will be a victory for dignity and decency, and for our common humanity. It will be a victory for the United States of America."

It was the president's first visit to a church in Washington, D.C., since Oct. 11, though the White House says Obama attends the Evergreen Chapel in Camp David when he visits the presidential retreat in rural Maryland.

Democrats are working furiously to reach an agreement on the massive bill as they watch closely the prospect of Coakley losing the seat held by the late Sen. Ted Kennedy to Republican Scott Brown. Brown has pledged to be the 41st vote against health insurance reforms. The election is Tuesday.

Democrats eyeing the possibility of losing the 60th seat needed to stop a Republican filibuster of the bill have suggested the Senate may try to pass a deal with only 51 votes rather than 60.

"Reconciliation is an option," Democratic Congressional Campaign Committee Chairman Chris Van Hollen of Maryland told Bloomberg Television. Reconciliation is a process that allows the majority to reduce the number of votes needed to pass unpopular tax increases and spending cuts if it means cutting the deficit, which the bill claims to do.

But liberal Democrats like Rep. Barney Frank say such a plan will kill the deal because it will limit policy changes that aren't incidental to the deficit cutting. It also requires resubmitting the bill back to the jurisdictional committees for revision.

On Thursday, Democrats working with President Obama agreed to exempt union workers from the 40 percent tax on high-payout plans that many high-risk workers are provided by employers.

Senate Minority Leader Mitch McConnell, R-Ky., said the exemption is aimed at getting more workers into unions.

"This is just another special deal for a favored constituent," McConnell told "Fox News Sunday." "It encourages people, actually, to join unions, presumably, because they would get better treatment from the government on their health care proposal."

McConnell noted that only about 7 or 8 percent of the private sector workforce is unionized, which means many workers are left out of the deal-making.

"What about all the workers who are not in labor unions? Why don't they get a special deal?" he asked.

Another negotiation hurdle was cleared last week when Nebraska Sen. Ben Nelson told Democratic leaders he no longer wanted the so-called "cornhusker kickback" that would have exempted his state from Medicaid co-payments. A likely replacement plan would bump up the federal money for Medicaid in all states.

Once a final deal is struck, the bill has to be priced out by the Congressional Budget Office. President Obama has said he wants to keep that under $900 billion over the next 10 years. However, the bill was already pushing that limit before the tax exemptions and increased Medicaid payouts were included.

But Democratic lawmakers trying to cut a deal are finding the sausage-making is rubbing many Americans the wrong way.

The latest Fox News poll found that 39 percent of Americans approve of the health care negotiations going on right now while 51 percent approve. That survey of 900 registered voters taken Jan. 12-13 had a margin of error of 3 points.

A similar Quinnipiac poll taken Jan. 5-12 of 1,767 registered voters found 34 percent mostly approve of the health care deal in the making while 54 percent mostly disapprove.

Democratic leaders are stressing unity.

"There are no sticking points. I would say if there's two words to the -- three words toward -- finding common ground, that's what we're in the process of doing," House Speaker Nancy Pelosi said Friday.

But McConnell, R-Ky., said no matter how the legislation ends up, it will hurt Democrats in November.

"I think the politics are toxic for the Democrats either way. This arrogant attempt to have the government take over one-sixth of the economy, on the heels of running banks, insurance companies, car companies, taking over the student loan business, doubling the national debt in five, tripling it in 10," McConnell said. "You've got ... sort of widespread public revulsion to this program."

Fox News' Caroline Shively contributed to this report.