Glass jaw

"How was I to know that big ape had a glass jaw?"

Early in Ali's career, experts believed he had what's called a glass jaw—that he would fall after the first big punch. He was now proving that he could take a punch, but each punch chipped away at his health.

It is essential that a player be able to identify his glass jaw or his weak spot and learn to deal with it in actual competition.

But if Obama does have a glass jaw, if his candidacy is a bubble waiting to be pricked, a strong Republican nominee like McCain is precisely the guy to do it.

Does the frontrunner have a glass jaw? All year, Biden has led in the vast majority of national and early-state polls of Democratic voters.