Mr. Duncan, a Republican, said late Wednesday he went to vote earlier in the day but ended up staring at the “most disappointing ballot” he’d ever seen in the matchup between Democratic Sen. Raphael Warnock and Republican challenger Herschel Walker, a former football star endorsed by former President Donald Trump.
“I had two candidates that I just couldn’t find anything that made sense for me to put my vote behind,” Mr. Duncan told CNN. “So, I walked out of that ballot box showing up to vote, but not voting for either one of them.”
Mr. Warnock and Mr. Walker are heading into a Dec. 6 runoff because neither secured the majority on Election Day.
A Warnock win would expand the Democrats’ Senate majority from 50 seats to 51.
Mr. Duncan recently blamed Mr. Trump for the GOP’s worse-than-expected showing in the midterms, saying the “drag factor” around the ex-president is real and “only getting worse.”
The lieutenant governor also wrote an opinion piece in mid-November urging Mr. Walker to seek victory by making three calls: One to Mr. Trump to beg him to stay home at Mar-a-Lago, and one each to Georgia Gov. Brian Kemp and Florida Gov. Ron DeSantis to get them to campaign for him.
Mr. Kemp has campaigned alongside Mr. Walker ahead of the runoff election, but Mr. DeSantis has not.