University of Minnesota law professor Richard Painter, once an ethics lawyer under a Republican president, said Monday in launching a U.S. Senate bid as a Democrat that the main target of his campaign would be President Donald Trump.

"I am going to fight alongside Minnesotans and Americans to do what is right to save our democracy from Donald Trump," Painter said Monday at a State Capitol news conference.

"I'm out of the Republican Party," he said. "I'm fed up."

Painter, who worked in the administration of George W. Bush, is running for the seat vacated by Al Franken and now occupied by Sen. Tina Smith. His intent, he said, is to offer an alternative to Smith in the DFL primary in August.

Nick Leonard, a Minneapolis lawyer and activist, announced in February that he would challenge Smith for the DFL nomination.

Michael McAdams, a National Republican Senate Committee spokesman, called Painter, a frequent critic of the president on TV and social media, a "Trump-hating impeachment advocate."

Painter's rejoinder: "I don't hate Donald Trump. I love America. He's unfit for office."

Sen. Karin Housley, the Republican candidate for the seat, criticized Painter's stance on Trump.

"Mr. Painter has repeatedly called for the impeachment of President Trump, an extreme notion deeply unpopular with many in our state," Housley said in a statement.

"Senator Smith is focused on working hard and being a strong advocate for the people of Minnesota, and she looks forward to earning and asking Minnesotans for their support," Smith's campaign said in its own prepared statement.

Painter called the influence of money "a serious problem in both political parties" and said he won't accept donations from political action committees or Super PACs.

Smith "should be a lot more willing to stand up" to the president, Painter said. He said he's willing to speak at the DFL Party convention in Rochester in June but would continue his campaign if he does not win the endorsement.

Chairman Ken Martin said the DFL Party welcomes Painter. "We look forward to endorsing a candidate — coming out of the State Convention unified and ready to take on the Republicans to keep this seat in DFL hands," he said in a statement.

Painter said he considered running as an independent but concluded that would divide DFL voters and help Housley, a small-business owner and suburban state senator. "A primary in August is not going to harm the Democratic Party," Painter said. Housley is the only Republican candidate.

Besides Trump, Painter said his campaign would also focus on issues including the jobs, the economy, the environment and health care.

He touched on other issues, saying that he thinks women's reproductive choices, including abortion, are "none of the government's business." Painter said he backs reasonable gun regulations and raising the age for gun purchases from 18 to 21. On health care, he said the country must find a way to cover all Americans.

Painter, 56, is married and has three children. The Philadelphia native graduated from Harvard and then Yale Law School. He was Bush's ethics lawyer from 2005-2007.

He is vice chairman of Citizens for Responsibility and Ethics in Washington. That group sued Trump, alleging that he violated the Constitution's emoluments clause by refusing to sell his assets or put them in a blind trust. The case was dismissed in December.

Judy Keen • 612-673-4234