Prominent DFL attorney David Lillehaug will don the black robe of a Minnesota Supreme Court justice in June, adding a longtime Democratic partisan’s voice to the high court’s Republican-appointed majority.

Gov. Mark Dayton, in announcing his selection Tuesday, described the white-haired, Harvard-trained attorney as “one of the most brilliant minds I have ever encountered.”

A former U.S. attorney for Minnesota, Lillehaug has been a legal and political force for years. He sued the state over churches’ rights to ban guns, represented U.S. Sen. Al Franken in a 2008 recount that lasted until 2009, and counseled Dayton in his 2010 recount, the 2011 state government shutdown and the Democratic-Farmer-Labor Party in last year’s redistricting.

Now, Lillehaug says, he will leave all that behind.

“My life will change for good,” said Lillehaug, who also made a brief run at elective office in 2000, when he sought endorsement in the U.S. Senate race that Dayton ultimately won. “I will leave behind the world of advocacy and I will swear a solemn oath to be fair and impartial. I will be one of seven justices doing justice, not based on politics and personalities but based on precedent and principles.”

Lillehaug, who handles complex litigation at the Fredikson & Byron firm, will replace Justice Paul Anderson, who reaches the mandatory retirement age of 70 in May. Governors’ Supreme Court nominees do not require legislative confirmation, but must stand for election at the end of their terms, which means Lillehaug will face his first elective test in 2014.

Unlike the U.S. Supreme Court, appointing party activists to the state court has become common in recent years. Anderson defended that practice.

“Don’t let anybody take any shot at you because you’ve been involved politically,” Anderson told Lillehaug on Tuesday. “We need people who have been in the trenches.”

Former Republican Gov. Tim Pawlenty appointed Christopher Dietzen, who had served as Pawlenty’s attorney during the 2002 gubernatorial campaign, first to the appeals court and then the Supreme Court. Justice G. Barry Anderson was the attorney for the Minnesota Republican Party before Pawlenty named him to the court. Retiring Justice Paul Anderson worked closely with former Republican Gov. Arne Carlson before Carlson elevated him to the bench.

“How do you get appointed to the Supreme Court? Know the governor, know the governor, know the governor,” said attorney Erick Kardaal, who has worked on the opposite side of cases from Lillehaug.

Lillehaug has cut a lower profile since last year, when he first applied to join the Supreme Court to replace retiring Justice Helen Meyer. That time Dayton selected appeals court Judge Wilhelmina Wright, who became the high court’s first black female member, and whom Lillehaug hired when he was U.S. attorney.

Dayton now will have appointed two of the court’s seven justices, but that is no guarantee of judicial outcomes.

“You don’t get to decide the cases just because you appointed the judge,” said Peter Knapp, a professor at William Mitchell College of Law.

Former Minnesota Supreme Court Chief Justice Eric Magnuson, a Pawlenty appointee who left the bench in 2010, agreed.

“It’s one thing to be an advocate, or passionate about a cause. It is quite another thing to be the decision-maker, where you have to balance the interests of everyone,” Magnuson said. “If someone is true to their judicial oath, you shouldn’t see a whole lot of difference based on philosophy.”

Magnuson noted that the high court has a moderating effect on those seated there.

“You’ve got to get three other people to agree with you,” he said.

In one of the last cases before he left the court, Magnuson faced the man who appointed him in an unallotment case that dealt with the separation of powers between Pawlenty and the DFL-led Legislature. Magnuson was part of a 4-3 majority that ruled against Pawlenty. Lillehaug argued the winning side of that case.

Lillehaug’s political connections run even deeper than those he will join.

Along with representing Democratic candidates and officeholders, the former debate team and moot court star has been a go-to operative for debate prep with candidates in major races, often playing a role in developing the lines that ring for years. He was a staff person for former Vice President Walter Mondale’s 1984 presidential campaign and worked with late U.S. Sen. Paul Wellstone and his campaign.

After Wellstone was killed in a plane crash days before the 2002 election, Lillehaug proved a calming influence as Democrats geared up to finish the campaign with Mondale on the ticket as a last-minute substitute, said Ken Martin, current DFL Party chairman, who also ran Lillehaug’s 2000 U.S. Senate campaign.

“David is probably one of the smartest men I know,” Martin said. “Not just in a book-smart kind of way, but he also has very good political instincts.”

Although politics has never been far from Lillehaug’s work, the South Dakota native has made his living largely outside the political fray.

As a Clinton appointee to the U.S. attorney’s office, he garnered early and sometimes unflattering attention for taking on high-profile cases against Qubilah Shabazz, Malcolm X’s daughter, and famed surgeon John Najarian in the 1990s. But he also shaped the office’s criminal prosecutions of gang leaders and white-collar criminals, including a case that ended with a former developer receiving one of the longest sentences imposed in the country at the time.

“He has great experience in civil litigation as well as criminal procedure,” said Rick Morgan, now an attorney for the Minnesota Republican Party.

Morgan, like many who have known Lillehaug, said he expects him to excel at the new job.

“My preference would be that Dayton would pick a Republican,” Morgan joked. But if that were not to be, Lillehaug was the next best choice.