Louisville, Kentucky - Candidates for U.S. Senate traded barbs on Thursday in hopes of winning the support of hundreds of local-level political leaders who will be instrumental in next May's primary election.

While Rand Paul questioned fellow Republican Trey Grayson's reading skills, Democrats Daniel Mongiardo and Jack Conway sparred over choices for personal financial investments.

They are running for a seat being vacated next year by Republican Jim Bunning.

Five lesser-known candidates shared the spotlight with the perceived front-runners at a forum sponsored by the Kentucky Association of Counties, hoping to get noticed by some 400 of the states' judge-executives, commissioners, magistrates and other local officials who filled a ballroom at the Galt House Hotel and Suites in downtown Louisville.

One of those candidates, Louisville businessman Maurice Sweeney, urged some 400 county-level political power brokers to look for new leadership.

"Leaders lead," Sweeney said. "Some of our career politicians couldn't lead you out of a paper bag."

That comment came shortly before Paul and Grayson had a testy exchange on the issue of Guantanamo Bay. Grayson claimed that Paul on his Web site supported the closure of the Guantanamo Bay prison camp where terrorist suspects are being held.

Paul said he is opposed to closing the Cuban facility and he also opposes the Obama administration's plan to put terror suspects on trial in federal court in the U.S.

"Then, I guess you'll have to change your Web page," Grayson said.

"You might learn to go read," Paul retorted, drawing laughs from the crowd.

He later apologized, saying: "I shouldn't have lost my cool."

Paul's campaign Web site had a position statement posted in May that said he agreed with a call to shut down Guantanamo Bay. Paul said two former campaign workers had posted the item without his knowledge.

"They were let go," he said. "They no longer work for us."

Mongiardo and Conway, both of whom tout their support for Kentucky's coal industry, charged each other with making private investments in energy companies that compete against coal.