"Heavens to Betsy," it's hard to believe that the John Kerry (search) of U.S. Senate stiff-speak is out there on the campaign trail tossing off homespun phrases, and even a joke or two.

Not only is the sometimes aloof senator from Massachusetts dropping an occasional laugh-line into his stump speech, his audiences are chuckling. This heartens campaign aides who think his message is extraordinary but worry that the delivery is often ordinary.

Even while speaking on the very serious topic of Iraq last week at New York University, Kerry made the audience laugh six times at President Bush's expense. Most of the guffaws came when Kerry stated Bush administration positions in a tone that suggested they were the height of ridiculousness.

Kerry said the occupation of Iraq is riddled with problems, "yet today, President Bush tells us that he would do everything all over again, the same way." Kerry paused for affect before asking sarcastically, "How can he possibly be serious?"

Sarcasm is a change for a man whose political career has been dominated by nearly 20 years in the Senate — the country's oldest deliberative body — with stern rules and mores for speaking that can make the people who work there unintelligible in heartland America. He has acknowledged that he has struggled not to fall into inside-the-Beltway language, and often his Capitol Hill training has won out.

But there are signs that Kerry is improving in the crucial closing weeks of the campaign. Like on Monday, when he predicted the president would continue to paint a rosy picture of the ailing economy, Kerry used an idiom likely to be heard among teenagers in a shopping mall, but not on the Senate floor.

"You're going to hear all this talk, 'Oh, we've turned the corner, we're doing better, blah, blah,"' he said, running on the phrase as his Wisconsin audience erupted in laughter. "You know, blah and blah and blah."

Kerry isn't just using the lingo of the younger generation. He's thrown in a couple of old-fashioned folksy phrases, too. "Heavens to Betsy," he said earlier this month when remarking on Republicans' failure to reinstate the assault weapons ban. "You bet your boots I know what I'm talking about," Kerry said Monday when promising to be more fiscally responsible than Bush.

Bush has been effectively using humor to mock Kerry throughout the campaign. He often delights Republican audiences by poking fun at his challenger by calling him a flip-flopper. "He probably could spend 90 minutes debating himself," Bush said with a chuckle Monday in Ohio.

Kerry was cracking up his partisan crowd by telling Wisconsin voters they shouldn't be wary of changing horses midstream when the horse is drowning. He tied the metaphor to reports that the Bush campaign insisted that podiums in Thursday's debate be set relatively far apart to obscure Kerry's five-inch height advantage.

"May I also suggest that we need a taller horse?" he said. "You can get through deeper waters that way."

But Kerry still slips into his comfortable old Senate-speak sometimes. On Monday, he boasted of his role in the Conservation Security Act that Sen. Tom Harkin (search) helped pass, without pausing to think that Wisconsin voters might not recognize that Harkin is the junior senator from Iowa.

But he drew guffaws at Temple University last Friday when he criticized Bush for dragging his feet before appearing before the Sept. 11 commission "but only with Vice President Cheney at his side." And he told late-night host David Letterman last week that Bush only agreed to debate if he could sit on Cheney's lap.