The standoff could wreak havoc with the U.S. economy
The plan involves raising taxes on corporations and the wealthy, using the funds to expand government programs
The next step is narrowing the menu of tax possibilities, focusing on measures likely to pass
The proposed top tax rate would revert to 39.6% on couples earning more than $450,000
Most Republican senators oppose increased spending
The Senate is likely to pass the $2 billion measure Wednesday afternoon