The fund invests in municipal securities that are exempt from regular federal and Minnesota personal income taxes. The fund invests at least 80% of its managed assets in investment grade securities rated, at the time of investment, investment grade (Baa/BBB or better by S&P, Moody's or Fitch) or, if they are unrated, are judged to be of comparable quality. The fund may invest up to 20% of its managed assets in municipal securities that, at the time of investment, are rated below investment grade or are unrated but judged to be of comparable quality. No more than 10% of the fund's managed assets may be invested in municipal securities rated below B3/B- or that are unrated but judged to be of comparable quality. The fund uses leverage.