BLACKSBURG - Democrat Tim Kaine is testing a new strategy he hopes will prevent Republican George Allen from overtaking him in Virginia's hotly contested U.S. Senate race. It's built around his son.

Nat Kaine, 22, recently graduated from George Washington University ROTC and is now a Marine Corps reservist who begins active duty in January. He's also proof, Tim Kaine said, that he wouldn't gut the Pentagon's budget, as Allen charges.

"You and I are both fathers," Kaine told Allen during their final debate last week. "I have a son who has started a career in the military. I will not do things that will hurt the troops or defense. I will not do things hurting veterans."

The strategy is Kaine's latest effort to combat a central argument of Allen's campaign: that Kaine supports looming defense cuts that would devastate Virginia's economy. Allen features the charge regularly in his ads and stump speeches.

Kaine denies the accusation but is clearly worried that it could undermine his support in voter-rich Northern Virginia and Hampton Roads, where local economies depend on defense spending.

At the heart of Allen's charge is a deal struck last year by Congress and the White House that raised the country's borrowing limit in exchange for a $1 trillion reduction in the federal budget deficit. Kaine supported that deal, which would allow $1 trillion in automatic budget cuts, half from the defense budget, to kick in if Congress doesn't reach a deficit-reduction deal by year's end. So far, no such deal has been reached, though Kaine said he hopes it will be, thereby avoiding the automatic defense cuts.

This isn't the first time Allen's political opponent has invoked a son's military service on the campaign trail. Sen. Jim Webb, a Democrat who took Allen's seat away from him in 2006, talked often of his son's service and even wore his son's combat boots while campaigning.

"I can only imagine what was running through George Allen's mind when Kaine said that about his son," said Craig Brians, a political science professor at Virginia Tech. "Allen has to be thinking, 'Is this another guy who's going to go to speeches with boots in his hands?' "

It's not clear whether Nat Kaine will become a regular feature of his dad's campaign. A senior Kaine aide said the family was hesitant to even mention Nat.

"Its something they're immensely proud of but don't view in a political context," said Mo Elleithee.

So far, Kaine's new tack hasn't quelled Allen's attacks on him. Allen said Kaine's support for a tax increase as part of any deficit-reduction deal will prevent a compromise and virtually guarantee the defense cuts.

"The men and women in our Armed Forces should never be used as a political bargaining chip to raise taxes on job-creating small businesses," Allen said.