Sen. Clinton has a very difficult task.

Convince voters it's necessary and worthwhile to risk a divisive, messy convention. Make the race about something different than it is, without crudely attacking Sen. Obama and having it backfire.

It's difficult to make this race about something else than it currently is.

It was difficult for Clinton's competitors to do it last year, because there are limited openings to stress policy differences. (Obama's big, and lucky, break was when Clinton finally made a debate mistake back in October, renewing fears of her electability.)

Clinton hoped one-on-one debates would be her salvation. Aside from that October debate, they have been her strong suit -- the forum where her fluidity in discussing policy shines, where she can best make the case she is the most prepared to be president.

But now, that plan requires Obama making a mistake. Instead, his debate performances get better and better.

He becomes a more confident and assuring presence, as he increasingly blends his inspiration and his wonk.

Clinton ended the performance on a strong, graceful note, stirring speculation that perhaps she won't go scorched-earth in the last weeks.

There's no need for her to muzzle herself. Principled attacks on policy -- like her arguments on health care mostly are -- are perfectly appropriate, and are the sort of thing that can turn a race around.

Though the health care argument alone has proven not to be enough. If that can't work in Russ Feingold country, it won't work in Texas or Ohio.

But more personal attacks, like those about his speeches, won't change what the race is about. They will just continue to backfire and diminish her reputation.

What other opening is there that can turn the race around for her?

Well, that's the problem.