The Wall Street bonus tax did not survive today in Congress. But its backers insist it may not be altogether dead.

Democratic Sens. Jim Webb of Virginia and Barbara Boxer of California had proposed a one-time 50 percent tax on bonuses of more than $400,000 awarded by the 13 firms receiving the most federal bailout money. Targeted firms included JPMorgan Chase & Co. and Goldman Sachs.

As we reported this morning, Webb and Boxer were pushing to have the tax attached to a roughly $150 billion bill that would extend unemployment benefits and tax credits. The bill cleared an important procedural vote today, but the bonus tax was left behind.

The bonus tax could still be introduced as an amendment to another bill, congressional sources say, including the Senate’s upcoming financial regulatory reform overhaul.

"We're not done trying to get a vote," Webb said on MSNBC this afternoon.