John Rich called Clay Aiken "racist" after the latter sent out a tweet saying he was playing a drinking game while watching the 2012 Republican National Convention.
"Playing drinking game with my brother now," Aiken, a former American Idol runner-up, tweeted to his 41,107 followers. "We drink every time we see a black person on screen at the RNC convention. #soberasamormon"
Rich, a Republican who has 105,408 Twitter followers, retweeted the message and accused Aiken of being a "racist."
In a series of tweets, he wrote: "CLAY! You should be ashamed for racist comments like THAT! WOW. ... I wonder how long it will be till @clayaiken takes that idiotic post down. Clay, you're better than that...I hope. Sincerely, JR. ... And to finish it off, @clayaiken hashtags soberasamormon? I thought your charity was for inclusion, not EXCLUSION. What happened?"
Aiken, who didn't delete the tweet, then replied: "My charity is. Why isn't your party? ;-)"
Aiken and Rich are both former contestants on The Celebrity Apprentice. Aiken, who came in second earlier this year, played for his charity the National Inclusion Project, while Rich, who won the 2011 edition, played for St. Jude Children's Research Hospital.
As a past winner, Rich returned to the NBC reality show this past season to interview the four finalists, including Aiken, and give recommendations to host Donald Trump on who should be fired. Aiken came in second to ultimate winner Arsenio Hall.
Rich, part of the country duo Big & Rich, currently is serving as a mentor on The CW's singing competition The Next.
On Wednesday, Yahoo News' Washington bureau chief David Chalian was fired two days after he made a racially tinged joke that was aired over the Internet during ABC News' online RNC coverage.
Referring to the RNC's concurrence with Hurricane Isaac's threat of the Gulf Coast -- the party canceled the convention's first day on Monday -- Chalian said: "They [the Romneys] are not concerned at all. They are happy to have a party with black people drowning."