Bill Clinton's hand appeared to tremble as he campaigned for his wife in Iowa, raising questions about his health.

Observers noticed that his fingers appeared to shake as he delivered a speech over the weekend to a crowd of 5,000. In the past, he's said it's simply a condition of aging.

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In 2013, Clinton denied he had Parkinson's disease, saying: "I have a condition that sometimes you get with aging. You may have noticed it; my hand has a little tremor when I’m tired and a lot of people do when they’re older.”

During the 69-year-old's speech, he explained why his wife partnered with Wall Street after the 9/11 attacks.

He said: “She was making the point that the people devastated on 9/11 were people to her, not categories.”

Bill Clinton was also a topic during the Democratic debate on Sunday night. Senator Bernie Sanders was asked to explain his recent comments about the former president.

Moderator Andrea Mitchell asked Sanders: “You've called Bill Clinton's past transgressions 'totally, totally disgraceful and unacceptable.’ Senator, do you regret saying that?”

Sanders hit back: “That question annoys me... Yes, his behavior was deplorable.  Have I ever once said a word about that issue? No, I have not. I'm going to debate Secretary Clinton, Governor O'Malley, on the issues facing the American people, not Bill Clinton's personal behavior."

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Hillary Clinton only discussed what role her husband would play in her administration, saying: “Well, it'll start at the kitchen table, we'll see how it goes from there.”

She added: “I'm going to use him as a goodwill emissary to go around the country to find the best ideas we've got, because I believe, as he said: ‘Everything that's wrong with America has been solved somewhere in America.’”

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