WASHINGTON—A federal appeals court on Friday refused to overturn the conviction of the only lobbyist to go to trial on charges of bribing public officials related to the Jack Abramoff scandal.

Kevin Ring's conviction was upheld by the U.S. Circuit Court of Appeals for the District of Columbia, which called his arguments on appeal "weighty," but not enough to overturn his conviction and sentence of 20 months in prison.

Ring got one of the stiffest terms among the 21 defendants in the investigation. Ring was the only lobbyist defendant to go to trial rather than reach an agreement with the government to plead guilty and cooperate. All the other lobbyists and most of the public officials charged cooperated with prosecutors and received plea deals, most of which did not include prison terms. Abramoff, the ringleader, pleaded guilty and was sentenced to four years in prison.

Ring, who worked under Abramoff, was convicted of giving meals and event tickets to public officials with an intent to corrupt them. Trial Judge Ellen Huvelle allowed evidence of legal campaign contributions, which prosecutors said showed how Ring gained access to public officials. But Huvelle also told jurors they could not consider the contributions as part of the "illegal stream of benefits" Ring was charged with providing officials.

Ring complained that Huvelle overstepped by allowing the legal contributions as evidence. But the appeals court refused to overrule her.

"We cannot say that the district court abused its discretion by concluding that the evidence's probative value was not 'substantially outweighed' by its prejudicial tendencies," Judge David S. Tatel wrote in the opinion. He was joined by Judges Janice Rogers Brown and Thomas B. Griffith.

Ring's first trial ended in a hung jury, but he was convicted in a second trial two years ago of five felony counts including conspiracy, payment of a gratuity and honest services wire fraud. He's been free pending the outcome of his appeal.

Ring was convicted of helping arrange a $5,000-a-month job for the wife of his former boss, then-Rep. John Doolittle, R-Calif., for which she did little work, and of corrupting two public officials with his gifts. Those officials included an aide to John Ashcroft, attorney general under President George W. Bush, and the then-chief of staff to ex-Rep. Earnest Istook, R-Okla. Ring took them out to expensive restaurants and gave them tickets to sporting events and concerts.

The gifts themselves were not illegal when Ring gave them. Jurors convicted him because they determined he gave them with an illegal intent to corrupt the public officials. In response to the Abramoff scandal, Congress passed a law in 2007 prohibiting lobbyists from giving such gifts.