WASHINGTON —  A Senate hearing that began with glowing tributes to a St. Louis businessman and his qualifications to become ambassador to Belgium turned bitterly divisive Tuesday after he was criticized for supporting a controversial conservative group.

Sen. John Kerry, D-Mass., grilled nominee Sam Fox about why he donated $50,000 to the Swift Boat Veterans for Truth during the 2004 presidential race. The group of Vietnam veterans made unsubstantiated allegations against Kerry — then the Democratic presidential nominee — and charged that Kerry did not deserve the medals he won in the Vietnam War.

"Might I ask you what your opinion is with respect to the state of American politics as regards the politics of personal destruction?" Kerry asked near the end of the hearing before the Senate Foreign Relations Committee.

Fox, one of the nation's most generous contributors to Republican candidates and causes, said he shared Kerry's concerns that politics "has become mean and destructive."

Fox said he didn't recall who asked him to give to the group and blamed partisans on both sides for contributing to so-called 527 groups that are not subject to conventional campaign finance rules.

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"So is that your judgment that you would bring to the ambassadorship, that two wrongs make a right?" Kerry asked.

"I did it because politically it's necessary if the other side's doing it," Fox said.

Fox said he played no part in crafting the Swift Boat message and called on Congress to ban or more carefully regulate 527s.

But Kerry said the incident raised questions about Fox's fitness to serve as an ambassador.

The back-and-forth overshadowed the early part of the hearing, in which a bipartisan group of lawmakers offered glowing reviews of Fox.

Sen. Barack Obama, D-Ill., a presidential hopeful and chairman of Tuesday's hearing, said he found Fox's responses "unsatisfying." He said he would have preferred if Fox admitted it was a mistake to contribute to the Swift Boat group.

Fox, 77, is founder and chairman of the Clayton, Mo.-based Harbour Group. He was deemed a "pioneer" by President Bush's campaign for helping to raise at least $100,000.