Joe Walsh, the former Tea Party congressman and 2020 Republican primary challenger to President Trump, said in an interview with BuzzFeed News that his past tweets calling former President Obama a Muslim are his biggest regrets on the platform.

Why it matters: While Walsh has apologized for some of his rhetoric, his inflammatory record is littered with controversy — including statements he has admitted were racist.

When asked about his tweets, specifically the one calling Obama a Muslim, Walsh told Buzzfeed, "That one bothers me the most. And I look at it and I say 'What the hell.'"

"It's the tweet I most regret. I let my policy differences with Obama cause me at times to be personal in my attacks against him. No excuse, and all I can say is that I'm sorry."

Between the lines: Walsh clarified that he doesn't think it's an insult to be called a Muslim. "There's nothing wrong with being Muslim. The insult was that I'm accusing him of lying because he has said he's Christian. That's why I was so wrong to do it."

Walsh also addressed his previous comments where he argued that he would not call himself a racist, but that "[he's] said racist things on Twitter."

"Those of us in the public eye have to account for things we've said. I think we're all capable of being racist at times, even if not purposely ... all I can do is apologize for [the remarks]."

Worth noting: In the interview, Walsh also said he believes climate change is real and that "it's an issue that the Republican Party needs a seat at the table with."

Go deeper: Trump's tweets are losing their potency