Over their Tuesday lunch, Senate Republican leaders are discussing how to respond to the Obama administration's push for an $2 billion for the overwhelmed cash-for-clunkers program, and the key may be where the money comes from.

Senate Democrats have already started running the $2 billion appropriation through a hotline -- a process that involves surveying potential opposition to a piece of legislation. If no senator objects, a measure can be quickly approved by a unanimous motion.

But Senate Republican Conference Chairman Lamar AlexanderAndrew (Lamar) Lamar AlexanderSenate Health panel approves opioid bill The risk of kicking higher ed reauthorization down the road Maternal deaths keep rising in US, raising scrutiny MORE (Tenn.) said Republicans will almost certainly push to modify the legislation somehow, such as by making sure the money comes from already-approved stimulus money instead of simply adding to the national debt as called for by the legislation passed Friday by the House.

"I would suspect that if that bill is moved, there will be an effort to offer an amendment to say that if we pass it, that the House or the Senate cannot go back in and fill up the stimulus again with $2 billion in debt money," Alexander said. "We'll see what our options are."

Alexander acknowledged the program appears to be working.

"It's stirring things up. It's helping dealers, it's helping car companies. It's having an impact," he said. "Yeah, it's helping some."

-J. Taylor Rushing