The retirement of DFL Sen. Linda Higgins from her District 58 Minneapolis seat set off a game of musical chairs in one of the most staunchly DFL areas in Minnesota.

n the four months since legislative maps were released, political strategists and journalists have been scrutinizing the new House and Senate districts to determine which ones favor Republicans or Democrats and where the key battlegrounds will be in 2012.

A handful of August primary elections are heating up across the state thanks to the new redistricting map, an uptick in legislative retirements and widespread dissatisfaction with the job lawmakers are doing in St. Paul.

Minneapolis DFLers lost another legislator last weekend. Freshman Rep. Marion Greene, who replaced former DFL House Speaker and gubernatorial candidate Margaret Anderson Kelliher in the chamber, fell in an endorsement contest against DFL House colleague Frank Hornstein.

Rep. Joe Mullery is no stranger to primary battles. The eight-term DFL legislator from North Minneapolis has faced intraparty contests in each of the last two election cycles.

This week, a third DFLer filed to make a run for the seat, and at least two more Democrats are thought to be mulling runs of their own.

Architect and activist Raymond Dehn announced Monday on his Facebook page and in a news release that he will run for the House District 58B seat, which currently covers part of north and downtown Minneapolis.

Eight Minnesota legislative incumbents -- five DFLers and three Republicans -- are facing challenges from members of their own parties this year, not counting six incumbents who have said that they aren't seeking re-election and have fellow party members lining up to succeed them.

More than 14 months before the 2010 general election, 19 people have filed with the Campaign Finance Board to run for the state Senate in 16 districts, and 16 have filed to run for House seats.