Conrad: Passing extenders will be a struggle

The bill costs roughly $200 billion and extends measures like unemployment insurance as well as tax breaks benefiting businesses and individuals. 

A large portion of the package is not offset because many of its measures are considered to be emergency spending. Under pay-as-you-go rules, such provisions do not require offsets. 

One spending measure drawing considerable fire for being labeled an emergency is the "doc fix," which delays a cut in Medicare payments to doctors. The measure adds approximately $65 billion to the deficit. 

"I understand absolutely the need now to extend unemployment, to do COBRA [health insurance], and those to me are emergencies," Conrad said. "But when we start doing other things, that concerns me." 

Senate Democratic Whip Dick Durbin (Ill.) said the bill's passage is contingent on his caucus knowing its details. This was especially true for the tax increase on carried interest. 

"There's some senators asking questions of what's in there, how for does it go," he said. "And I think there has to be some clarity in the caucus before there [is] a commitment."