As Sen. Claire McCaskill (D-MO) put it at a press conference Tuesday, "Take the word 'shall' out and say 'if you don't it's really gonna cost you a bundle.'"
There was once bipartisan support for this structure -- though there was also once bipartisan support for the mandate itself. The question is whether Republicans would be willing to play ball on fixing the law when their goal is to bring it down completely.
"We did look... when we were trying to look at alternatives during the debate, at a defined enrollment period, which allowed people to sign up, but didn't make them sign up, but where there were penalties if they didn't sign up during that period," said Sen. Bob Corker (R-TN). "We had studies done that said that that in fact could well solve the problem of people enrolling after the fact."
McCaskill wants more data. "The issue is will the research support that approach as workable to still allow us to cover people with pre-existing conditions," she said.
That would also moot the constitutional complaint against the mandate. However, don't expect Democrats to act on this unless it's truly necessary. As Sen. Chuck Schumer (D-NY) told reporters Wednesday, they can't really weaken the mandate much without badly undermining the bill.
"You'd have to look at the specific proposals," he said. "The bottom line is that if you change the mandate, one of two things will happen: Many of the good things in the bill will not be there, such as pre-existing conditions, or premiums will go way, way up."