Richard Painter, a University of Minnesota law professor and prolific TV and Twitter critic of President Donald Trump, said Wednesday that he is forming an exploratory committee that could lead to a campaign for the U.S. Senate seat vacated by Al Franken and now occupied by Democrat Tina Smith.

Painter said at a Capitol news conference that although he’s a longtime Republican and served as chief ethics lawyer in George W. Bush’s White House, he’s unsure whether he’ll run as a Republican, Democrat or independent.

“I need to think about whether there’s a place for me” in the GOP, he said. “I’m going to be considering any and all options.” He described himself as “a centrist in many ways — right up the middle.”

Karin Housley, a small-business owner and suburban state senator, is the only Republican to announce plans to run for the seat. She was elected to the Legislature in 2012.

On March 3, Painter tweeted that Housley had blocked him. “She’s upset that I asked her to talk about serious issues rather than blame 20 minute lines at DMV on her opponent Tina Smith. For example that wait at DMV is 20 minutes more than it takes to register an AR-15.”

“It’s important for voters to have a choice in any election, so we welcome our new opponent to the race,” Housley’s campaign spokesman Bryan Piligra said in a statement. “Karin Housley has given a voice to the many Minnesotans who are fed up with the dysfunction, partisanship, and obstruction in Washington. Having another extremist in the U.S. Senate will not end the plagued status-quo — they would make it even worse.”