His long tenure working for Democratic U.S. Rep. Betty McCollum began after the controversial 2000 presidential election and continued on past the Sept. 11 attacks, the Iraq War, the Great Recession, the outbreak of COVID-19 and the U.S. Capitol insurrection.

As he prepares to leave the job in January, Harper is aware that he was part of a transformative historical period. But he said in a recent interview about his more than two decades on the job that it all comes back "to serving the people and trying to make our democracy, and trying to make Congress, work for the people despite these enormous challenges that we faced."

Harper noted that he was part of the Peace Corps and spent time as an HIV/AIDS volunteer in Malawi before running McCollum's 2000 congressional campaign.

Said McCollum: "If anybody would have told us when we first met working on the campaign that 23 years later we would still be working together, we both would have just laughed out loud."

She said Harper is someone who does his homework, knows what he's talking about and has a very reassuring presence.

"When he says he's going to do something, he's going to do it, and he's a man of his word. And so that's how he's earned so much respect over the years," McCollum said.

During their time working together, McCollum has gone from freshman lawmaker to dean of Minnesota's congressional delegation. In November, she won a 12th term while Democrats narrowly lost control of the U.S. House. McCollum has wielded major influence in the past two years while leading the House Appropriations subcommittee handling defense spending.

"When you're at this level, you take the partisanship out of the equation and you focus on, 'This is about America; this is about our country,' " Harper said.

Democratic U.S. Rep. Dean Phillips called Harper "one of the most connected, principled, honorable and effective Capitol Hill staffers that I know of."

Looking back, Harper said the accomplishment that makes him proudest is his work with McCollum on President George W. Bush's emergency plan for AIDS relief in 2003.

"We secured language for orphans and vulnerable children," he said.

McCollum's office said in a news release when Harper's exit was announced that he will continue to work as a political adviser for the longtime Democratic lawmaker. Harper said he's interested in using his experience and skills to "work with nonprofits and businesses to help them advance their missions, particularly in the federal space."

As he prepares to leave Congress behind, Harper said that "as powerful as Washington and Congress may be, we are a direct extension of the people. And it needs to stay that way."