Factbox: Key players in final hurdle for Wall Street bill

(Reuters) - A landmark overhaul of U.S. financial regulations could receive its final approval in Congress this week, though Democrats in the Senate have not yet nailed down the votes to assure passage.

Three Republicans -- Scott Brown, Susan Collins and Olympia Snowe -- said on Monday they would support the bill.

Some 54 Democrats and two independents are also likely to support it, leaving Senate Majority Leader Harry Reid one vote short of the 60 needed to advance legislation in the 100-seat chamber. The House of Representatives has already passed it.

Reid hopes centrist Democrat Ben Nelson or possibly Republican Charles Grassley will decide to back the measure. Barring that, Reid might have to wait until next week to give West Virginia time to fill the seat left vacant by the death of Democratic Senator Robert Byrd last month.

Here are the lawmakers and other officials whose stand could be critical.

DEMOCRATIC SENATOR BEN NELSON

Nelson is one of the most conservative Democrats who frequently votes with Republicans on fiscal issues. Though he backed an earlier version of the financial-reform bill, he said on Monday he had not committed to vote for the final product.

"Mostly we're looking at what we don't know," Nelson told reporters on Monday. "When we figure out what we don't know it'll be helpful."

REPUBLICAN SENATOR CHARLES GRASSLEY

Grassley, from Iowa, was the lone Republican to vote for tough derivatives regulations drafted by the Agriculture Committee, and he voted for final passage on the Senate floor. But he had voted against it in an earlier procedural vote. Spokeswoman Jill Kozeny said he is "very concerned" that the bill covers its nearly $18 billion cost by raising deposit-insurance fees and tapping a bank-bailout fund.

WEST VIRGINIA GOVERNOR JOE MANCHIN

Manchin, a Democrat, is expected to name a Democrat who backs the financial-reform bill to temporarily fill Byrd's seat. But he will not act until he and other state officials have decided when to hold an election to fill the seat permanently, a process that could last into next week.

Manchin is interested in running for the seat eventually but has said he would not appoint himself as interim senator.

DEMOCRATIC SENATOR RUSSELL FEINGOLD

Feingold, one of the most liberal members of the Senate, is the lone Democrat to say he will vote against the bill. He has said it does not do enough to prevent future crises.

(Reporting by Andy Sullivan and Thomas Ferraro; Editing by David Storey)