A handful of Senate Democrats on Wednesday were pushing at the eleventh hour to make a sweeping Wall Street reform bill even tougher, but they were running out of time as a key procedural vote approached.

The bill, steered by Senator Christopher Dodd, would shift leftward under Democratic proposals that would, for instance, tighten limits on risky bank trading and break up financial giants.

Prospects for these and other proposals were dimming, however, as the Senate neared a 2 p.m. ET vote that would strictly limit further amendments and debate.

If the cloture vote is approved, a final vote on the bill's passage could come between Wednesday evening and Friday. Failure to impose cloture could push a final decision into next week, but Senate Democratic leaders were keen to wrap it up.

The bill, a top priority of President Barack Obama, would tighten rules for banks and capital markets to prevent a recurrence of the 2007-2009 financial crisis, which tipped the economy into a deep recession and triggered taxpayer bailouts.

Political momentum has been running heavily against Wall Street, which has fought for months to kill or weaken the bill only to see lawmakers further tighten the crackdown.

Politicians from both parties are eager to show voters they are getting tough on Wall Street before November elections.

Dodd has fended off other proposals from fellow Democrats that could upend the financial industry, but analysts expect the final product will still result in lower profits and tighter rules for banks and Wall Street.

The final bill will contain fundamentally tough reforms, creating many headwinds to banks' profitability, analysts at FBR Capital Markets wrote in a research note.

Few Republican amendments to weaken the bill remained in play. Among the most significant was a proposal by Senator Sam Brownback to exempt automobile dealers from a new consumer-protection bureau, which Republicans argue could saddle small businesses with onerous regulations.

Though the prospects for Brownback's amendment remained murky, Republicans appeared likely to fend off other proposals opposed by the financial industry.

They continued to block action on a measure to toughen rules that would prevent banks from trading on their own accounts and get them out of the hedge fund business.

That proposal, offered by Democrats Jeff Merkley and Carl Levin, would give regulators less leeway to interpret rules first proposed by White House economic adviser Paul Volcker, the influential former chairman of the Federal Reserve.

Democrats still had yet to resolve a major dispute of their own. The current bill would force banks to separate their lucrative swap-trading desks from their core operations, but Dodd hopes to give regulators more leeway to kill that rule if they determine it would harm the economy.

But he faced firm opposition from the measure's author, Agriculture Committee Chairman Blanche Lincoln, who faces a tough electoral challenge from the left in her home state of Arkansas.

Many analysts expected Lincoln's support to waiver after Tuesday's primary election. But Lincoln failed to win 50 percent of the vote against Lt. Gov. Bill Holder, setting up a June 8 runoff and pressuring her to keep up her anti-Wall Street stance.

(Reporting by Kevin Drawbaugh and Andy Sullivan; Editing by Jan Paschal)