When Republican U.S. Senate candidate Mike McFadden strode into St. Paul’s State Office Building to file his candidate paperwork last week, he greeted the waiting media and more warmly greeted the two Democratic trackers who follow his every move.

McFadden said he sees them everywhere.

“They work hard,” he said.

Trackers are the young partisan staffers who record candidates wherever they go to aid in opposition research, hoping to catch their prey in an off-message moment.

“That’s part of the process. It’s what I’ve signed up for. They’ve been very respectful,” McFadden said.

That respect sometimes grows.

Democratic U.S. Sen. Amy Klobuchar’s 2006 Republican tracker Ryan Flynn became a 2012 supporter when she ran for re-election.

But the relationships are not always so smooth.

In 2010, Mark Dayton, then running for governor, complained that his GOP trackers followed him so closely that they made it impossible for him to greet Minnesotans at Game Fair, an outdoors expo in Anoka County.

Republicans used the complaint to pound Dayton for having a “bizarre, weird, erratic reaction” and had T-shirts printed for their trackers with the message: “I’m with the guy who wants to raise your taxes.”

Rachel E. Stassen-Berger