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Obama appeared at a campaign rally in Boston for Democrat Martha Coakley, whose 30-point lead in the polls in December has vanished and who is now in a tight race with Republican Scott Brown before Tuesday's election.

Speaking to 1,500 supporters gathered in a basketball arena at Northeastern University, Obama ridiculed Brown for his populist campaign tactic of driving around Massachusetts in a pickup truck and attacked him for not supporting a bank bailout tax Obama proposed last week.

"We asked Martha's opponent, what's he going to do, and he decided to park his truck on Wall Street," Obama said. "Let me be clear: Bankers don't need another vote in the United States Senate. They've got plenty."

A victory by Brown would be a shock upset in the traditionally liberal New England state. At stake is the Senate seat held by the late Senator Edward Kennedy for 46 years, a fact that Coakley raised at the rally. "I need your help to follow in his huge footsteps," she said.

Aware that his healthcare push is generating some opposition in Massachusetts, Obama made little mention of his top domestic priority, choosing instead to emphasize Brown's opposition to the bank tax.

But the fact is that Obama's healthcare overhaul could be slowed if Brown wins since the Republican has vowed to vote against it.

DEMOCRATS COULD LOSE SENATE SUPERMAJORITY

By losing the Massachusetts seat, Democrats would lose their 60-vote supermajority, hampering their ability to cut off debate and proceed to a vote. They could resort to tactics to pass it by a simple majority, but that strong-arm route would carry some political risks.

"This is, in effect, a referendum on the national healthcare bill which the Democrats, in secret, are trying to work out now," Senate Republican leader Mitch McConnell told Fox News Sunday.

A Brown victory would embolden Republicans hoping to reduce strong Democratic majorities in the U.S. Congress in November elections.

A year after taking office with high hopes, Obama has struggled to restore job growth to the U.S. economy and has pursued healthcare legislation that many Americans regard with suspicion.

Obama, whose one-year anniversary this week has been accompanied by less-than-stellar reviews of his job performance, asked for patience at a church service before a largely African-American congregation in Washington.

"There are times when progress seems too slow. There are times when the words that are spoken about me hurt. There are times when the barbs sting ... But let me tell you -- during those times it's faith that keeps me calm," he said.

Obama was unable to save Democrats from defeat last November in elections for governors of New Jersey and Virginia and has his work cut out for him in Massachusetts.

A Suffolk University poll last week that gave Brown a 50-46 percent lead over Coakley prompted the White House to accept her request for Obama to visit Boston and try to drive up voter turnout.

Charlie Cook's non-partisan Cook Political Report declared the race a toss-up with Brown holding a slight edge.

"Last minute Democratic attacks on Brown have driven his negatives up some and slightly diminished the incredible intensity of support that Brown enjoyed, but it looks more likely than not to hold," it said.

"The voters will decide who wins this race based on the issues -- not big-named endorsements from the Democrat political machine," said Brown spokeswoman Tarah Donoghue. "Scott Brown has run a positive campaign on the issues like jobs and the economy."