Updated

Fred Thompson said Sunday that he wishes he had known earlier that one of his key presidential campaign advisers pleaded guilty to drug charges but he still thinks Phil Martin is "a good man."

Martin, a businessman who has lent Thompson his Cessna to fly around the country, is one of four campaign co-chairman for the '08 Republican candidate. The Washington Post reports Sunday that Martin also posted a guilty plea in 1979 for selling 11 pounds of marijuana and a no contest plea in 1983 for cocaine trafficking and conspiracy.

Judgment was withheld on the first plea while Martin served out probation. The 1983 charges, along with a felony bookmaking charge, came while he was still serving that probation. Martin's probation was extended and he served no jail time.

Click here to read The Washington Post article on Thompson donor Phil Martin.

Thompson, who's not the first candidate this year to be linked to a donor with a criminal past, seemed to brush off the news.

"You are talking about something that happened in his life, I guess, 25 years ago ... when he was in his 20s," Thompson said. "I wish I had known about it a little bit earlier. Phil, I am sure, knows that he should have told me about this. That he thought (it) was over and done with and forgotten about I am sure. But of course nothing is ever over and done with and forgotten about in this business."

Click here to see Thompson's remarks about his friend.

According to the Post story, Martin started out in Republican politics in Tennessee in the early 1990s, when he met GOP Rep. Zach Wamp. During fundraisers for Wamp, Martin got to know Thompson. He began donating to Thompson in 1994, during Thompson's first run for the U.S. Senate. Overall, from 1992 to 2002, Martin donated more than $75,000 to Republican candidates and causes in Tennessee, the newspaper says.

Martin "was always wanting to help candidates," Wamp told The Washington Post. "I assume through 10 years of political involvement, when Fred came on the scene, they immediately saw eye to eye."

Thompson communications director Todd Harris told the Post that the campaign didn't vet Martin because "he's a longtime friend."

"There's not a campaign in the world that has the ability to research every one of its supporters going back more than 20 years," Harris said.

The Post reports that Martin has also lent Thompson his plane for possibly two dozen campaign stops since the summer, for a price of $102,330. That's about half of what it would cost to rent a charter plane for those flights. The payment at a fraction of the commercial price was legal and common for many candidates until Congress passed lobbying and ethics reform rules in September.

Thompson said that none of the contributions raised by Martin, who's head of a group called "first day founders," are "improper." He did not indicate that he would return any of the funds from Martin.

"I know him to be a good man. I know him to be a man who has rehabilitated himself and has led a productive life. He is my friend and he is going to remain my friend. Now, what I do about it after I talk to him with regard to the future, we will just have to see," Thompson said.

Speaking on NBC's "Meet the Press," Thompson added, "He didn't go to jail, he (was) on probation, he paid his debt to society and turned himself around ... and is a successful citizen. ... I'm not going to through my friend under the bus, you know, for something he did 25 years ago."