Complex sentence: However, it has been represented since 1991 by DFLer Collin Peterson, a moderate rated 50% conservative by a conservative group and 57% progressive by a liberal group.
Split into simpler sentences: However, it has been represented since 1991 by Collin Peterson, a moderate-to-conservative DFLer. He is rated 50% conservative by a conservative group and 57% progressive by a liberal group.