Rep. Tim Walz doesn't appear to be taking anything for granted.

The Mankato Democrat took the unusual step this morning of sending debate invitations to his three challengers in the First District, a rare move for an incumbent member of Congress.

Campaign manager Richard Carlbom e-mailed a letter to Republican Randy Demmer, IPer Steven Wilson and independent Lars Johnson asking them to participate in three 90-minute debates before October 15.

Carlbom said Walz was also the first to breach the subject of debates in 2008, leading to three post-Farmfest events. Two of Walz's three proposed debates this year will have a specific focus -- jobs/economy and veterans/wars -- while the third will be televised (and presumably open-topic).

Carleton College political scientist Steven Schier called it a defensive maneuver for Walz, a two-term incumbent in a moderate outstate district.

"The best defense is a good offense," Schier said. Taking on all comers is also a savvy tactic, Schier said. "It takes the spotlight off Demmer, to an extent, by making him just another face in the crowd."

While Walz is not on anybody's endangered species list yet, Schier added, in a year that's expected to go badly for Democrats it's hardly realistic for his campaign to employ the usual Rose Garden strategy of ignoring the opposition.

"They're trying to build a firewall to prevent a national wave, which is coming, from washing him away. They believe they have to take action early."

Rep. Tim Walz and IP candidate Steven Wilson at Farmfest.

The Demmer camp did not immediately return a request for comment.

The southern Minnesota district is often considered one of the most moderate in the state, though Walz won handily in 2008 with 62 percent of the vote.

KSTP and the League of Women Voters have also arranged for the Third District candidates to debate next month.

Rep. Erik Paulsen's campaign manager Tim Commers said they will likely participate in the September 25th televised discussion with DFL challenger Jim Meffert. Meffert spokester Kate Monson said they will be attending as well.

- Kevin Diaz contributed to this report.

UPDATE: Demmer camp responds.