JACKSONVILLE — For 20 years, Tampa home builder Timothy Mobley and U.S. Rep. Vern Buchanan have been friends. They vacation together, bicycle together and at times have done business together.

Now that friendship has exacted a heavy toll, though not as heavy as federal prosecutors wanted. A federal judge in Jacksonville last week sentenced Mobley to three years' probation and fined him $200,000 for making illegal contributions to Buchanan's campaigns and the Republican Party of Florida.

It was the stiffest penalty so far to result from the numerous investigations into fundraising activities on behalf of Buchanan, a millionaire Sarasota car dealer.

Prosecutors had sought a prison term for Mobley, 60, saying he orchestrated a scheme to reimburse his employees and their relatives more than $90,000 for contributions to "Committee A" — Buchanan's campaign committee — and to Florida's Republican Party.

Such "conduit" contributions are illegal under federal law, which prohibits contributing in another person's name.

Mobley's scheme "undermined one of the core goals of the federal campaign finance law — transparency,'' prosecutors said in their sentencing memorandum. "The defendant deprived the public of its right to know who was funding campaigns and to what extent."

Arguing against prison time, Mobley's lawyers said that his friendship with Buchanan was purely personal and that Mobley "has absolutely nothing to do with Congress or the federal government.'' Several letters praising his character were submitted to the court, including one from Timothy Mobley Jr., now a senior at the U.S. Air Force Academy in Colorado.

Buchanan's office said he did not help the younger Mobley get into the academy, many of whose students are nominated by their senator or congressman. Although Mobley has built hundreds of homes in Hillsborough County, the Mobleys live in Manatee County, which is part of Buchanan's district.

Buchanan and his wife, Sandra, also have not provided any financial help to the Mobley family, a Buchanan spokesman said. In 2010, before Mobley was charged, one of his companies borrowed $2 million from a company headed by Sandra Buchanan, Hillsborough court records show.

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In February, Mobley's brother-in-law, Tampa accountant Timothy Hohl, was fined $15,000 after pleading guilty to making illegal contributions to Buchanan. And last year, Sam Kazran, Buchanan's former partner in a Jacksonville Hyundai dealership, was ordered to pay the Federal Election Commission at least $5,000 for reimbursing employees who donated to Buchanan.

Since his first campaign in 2006, Buchanan has been fighting allegations of illegal fundraising. Several former employees sued him, saying they were pressured into making contributions and illegally reimbursed. Most of the suits have been dismissed, but Buchanan's campaign has refunded more than $90,000 in contributions.

In an investigation involving the Jacksonville dealership, the FEC's general counsel said it was "more likely than not" that Buchanan violated election laws and concluded that many aspects of his testimony were not credible. The agency took no action, but the Office of Congressional Ethics is investigating allegations that Buchanan pressured Kazran, his former business partner, to lie in an affidavit.

Records show that Buchanan's campaign committee has spent more than $155,000 to resolve his legal issues and that Buchanan and his wife have sold millions of dollars worth of stock in the past year.

Buchanan, now in his fourth term, has repeatedly denied involvement in conduit contribution schemes, a claim that the nonpartisan Citizens for Responsibility and Ethics in Washington found hard to believe.

"If Rep. Buchanan is, in fact, innocent, he must be something of a dimwit," CREW officials said in a statement last year. "Why would his business partners, employees and car dealerships funnel conduit contributions to his campaign without his knowledge? Car dealers can't even throw in free floor mats with a purchase without calling their boss, but apparently, they can run elaborate conduit contribution schemes. The only person who stood to benefit from such contributions was Rep. Buchanan."

Susan Taylor Martin can be reached at susan@tampabay.com.