What does Democrat Hillary Clinton's laugh have in common with Republican Rudy Giuliani's cell phone?

Both are causing waves on the U.S. presidential campaign trail for the leading candidates in each party.

For Clinton, her tendency to burst out in a giggle during some public appearances has generated political tongue-wagging.

The New York senator, often seen as an overly serious candidate, has been showing some personality lately.

She laughed at times during questioning on Sunday morning television shows more than a week ago and then hooted with laughter when asked to respond to a critical comment from a rival candidate at a debate last Wednesday in New Hampshire.

It has become so frequent that Frank Rich, a liberal columnist for The New York Times, said the laugh seemed to be the Clinton campaign's method of heeding complaints that she is "too calculating and controlled" and compared it to Democrat Al Gore's long kiss with his wife Tipper during the Democratic National Convention in 2000.

"Now Mrs. Clinton is erupting in a laugh with all the spontaneity of an alarm clock buzzer," Rich wrote.

Comic Jon Stewart on "The Daily Show" last week likened her to a robot with a robotic voice saying, "Humorous remark detected -- prepare for laughter display."

Presidential scholar Stephen Hess of George Washington University said Clinton's ability to laugh indicated she was becoming more comfortable as a candidate.

Regardless of whether it is genuine or not, "It's terrific that you're able to laugh given what one goes through in a campaign," he said.


Then on the other hand there is the case of Giuliani and his cell phone.

It rang just as Giuliani was addressing the National Rifle Association recently, and he pulled it out of his pocket and chatted to his wife, Judith, in mid-speech.

The incident had some of the NRA members rolling their eyes and even some of Giuliani's supporters thought it was a silly display.

The former New York mayor has since explained the reason why he took the call and denied it was a calculated move -- even though reports circulated he had done it at least once before.

"Quite honestly, since September 11, most of the time when we get on a plane, we talk to each other and just reaffirm the fact that we love each other," he told the Christian Broadcasting Network.

Hess called it a bizarre incident.

"This man is a candidate for president talking to an important group, and it should have his undivided attention and you should at least turn off your cell phone," he said.