Nelson, a centrist Democrat who also broke with his party on healthcare legislation and several jobs bills, joined Republicans in opposing the legislation.

The vote this afternoon was a long-awaited procedural vote to begin formal debate on the legislation, Democrats' top legislative priority since returning from recess.

But after negotiations between Sen. Chris Dodd (D-Conn.), the chairman of the Banking committee, and Sen. Richard Shelby (R-Ala.), the ranking member, had hit snags over the weekend, the vote was expected to fall short.

A series of Republicans who had been seen as wavering on the bill stuck with the GOP on the vote, though all 59 Senate Democrats had been seen as likely to join together to support the bill.