BLOOMINGTON, Minn. (AP) _ A man wearing a rubber Richard Nixon mask robbed a bank in this Minneapolis suburb, and police suspect he is half of a duo that has used politicians' masks in 31 bank robberies since 1985.

The robber, armed with a semiautomatic pistol, ordered everyone in Norwest Corp. to freeze. He demanded cash and fled in a getaway car that had been stolen, the FBI said.

Just blocks away, he switched to another stolen car and disappeared. The FBI declined to say how much was taken.

Police say two men have worn masks of Ronald Reagan and Michael Dukakis during heists from suburban Chicago into Wisconsin since 1985.

The duo apparently started robbing banks in 1985, stopped after two robberies, then started up again in 1990, said Larry Mefford, bank robbery supervisor for the Minneapolis office of the FBI.

Authorities believe that 25 of the robberies took place in the Chicago area and six in Wisconsin, the most recent in La Crosse on Feb. 4.

Mefford said he believes the duo moved to Minnesota because Chicago authorities have been on their trail.