If the Court finds the mandate unconstitutional -- a big if -- it will either strike the mandate alone, toss out coverage guarantees that the mandate is meant to support, or throw the whole law out. Those are, at least, the three most likely possibilities.
Harkin says he's ready for all of them.
"We're going to have to have some kind of community rating and keep the guaranteed issue," he said. Those are the technical terms for provisions guaranteeing that all consumers can buy health insurance regardless of pre-existing conditions, and cost sharing to allow high-risk people to afford insurance.
"We have some possible legislative fixes that I will bring forth at that time," Harkin said. "But we are prepared for different forms of legislation to address that."
In the unlikely event that the Court throws the whole thing out, Harkin says he'll try to reanimate the whole thing.
"If they throw the whole thing out, yes, I will be prepared then with what I call a Health Care Restoration Act," he said.
This is considerably more detail than most top Democrats typically offer. "We're waiting, we're ready to move when the Supreme Court makes a decision," said Senate Majority Leader Harry Reid.
Harkin's fully aware that Republicans will block attempts to fix or restore the law, but he believes President Obama will be strongly positioned to demand action from Congress, particularly if he wins re-election.
"I think that Obama would be in a very good position of saying, 'Ok, here's our fixes, let's fix it now.'" Harkin said. "And if Republicans say now, well they'd have to answer for why everything else in the bill is going down and why premiums are skyrocketing."