In 1990, Senator Derr was not challenged and received 100% of the vote. In the 1994 primary election, Derr received more competition, this time from Republican Charles R. Luttrell. Luttrell managed to garner 47% of the vote. Derr went on to win the general election, this time, oddly enough, beating the same candidate, Charles R. Luttrell, who apparently switched parties to challenge Derr again.
In 1998, Derr saw the end of his senatorial career. He was defeated by Republican challenger Alex X. Mooney in the Republican primary election. Mooney received a sizable majority of the votes, 63% to Derr's 37%. Mooney went on to win the general election, defeating the Democrat candidate Ronald S. Bird.
Derr is a past president of the Frederick Jaycees , and was named Jaycee International Senator in 1977. He is also a past president of the Frederick County Heart Association. Derr belongs to the Frederick Life Underwriters Association and is a member of the board of trustees for Frederick Memorial Hospital
While serving in the Maryland State Senate, Derr rose to the level of the Minority Whip from 1996 until he was defeated in 1999. He was the Senate Chair for the Joint Committee on Protocol and he was the chair of the Frederick County Delegation from 1995 until 1999.
An article in the Washington Post suspected that Derr was defeated because of his view on abortion rights. F. Vernon Boozer suffered the same fate with his views on abortion and gun control in his loss to Andrew Harris.