Based upon their questions, some of the justices appeared to support his claim that his actions didn't rise to the level of a crime.
Chief Justice John Roberts suggested that the law might be unconstitutionally vague. And Justice Stephen Breyer said prosecutors might have too much power deciding when politicians' political favors become crimes.
Washington lawyer Noel Francisco, who represented McDonnell, said none of McDonnell's favors for businessman Jonnie R. Williams Sr. were "official acts" than can be considered bribery. McDonnell admits that he accepted more than $170,000 in gifts, loans and vacations, but says he didn't violate federal law because his actions were merely routine courtesies.
But Deputy Solicitor General Michael Dreeben, representing the government, argued that overturning the verdict "would send a terrible message to citizens."
Justices Sonia Sotomayor and Ruth Bader Ginsburg seemed to back the government's stance. Ginsburg said a government official would be able to say, "You want a meeting, pay me a thousand dollars" with the defense's interpretation of the law.
A federal judge sentenced McDonnell, 61, to two years in prison in January 2015 after a jury found him and his wife guilty of 11 counts of corruption.
McDonnell, who was governor from 2010-14, sat with his wife, Maureen, during the one-hour proceedings.
Afterward, he told reporters was grateful the case was heard.
"And I want to give credit to my Lord, Jesus, for his sustaining me and my wife and my family during these last 39 months that have been very, very difficult," McDonnell said. "And I want to say, as I've said for the last 39 months, that never during any time during my 38 years of public service have I ever done anything that would abuse the powers of my office."
McDonnell's conviction on 11 counts was upheld by the Fourth U.S. Circuit Court of Appeals in July.
"The government's interpretation of the statute is so broad that almost any major politician could be prosecuted. And of course they're not," John Jeffries, a University of Virginia law professor who is among legal experts who signed a brief backing McDonnell's legal arguments, told The Virginian-Pilot.
"It is unmistakably sleazy," Jeffries said. "I have not heard anyone who defends his conduct."