Election to Fill Seat in Assembly Set for April 11 : Legislature: Expulsion of GOP’s Mountjoy in speakership battle left vacancy. Vote in 59th District is expected to go to a Republican.

A special election is scheduled for April 11 to fill the Assembly seat formerly occupied by state Sen. Richard L. Mountjoy, expelled from the lower house in the recent leadership battle won by Speaker Willie Brown.

If no candidate receives a majority of votes in April, the race for the 59th District seat will be decided in a June 6 runoff, Gov. Pete Wilson announced this week.

The period for filing nomination papers opened Tuesday and closes Feb. 27, an election official said. No one had filed nomination papers as of Wednesday, but several current and former members of city councils in the district are expected to run for the seat.

The 59th District includes all or part of Arcadia, Claremont, Covina, Duarte, Glendora, La Verne, Monrovia, Pomona and San Dimas.

A Republican is expected to win in the 59th District, where 47.8% of the registered voters are Republican and 39.6% are Democratic. If that happens, the Assembly’s Republican Caucus will regain the seat lost on Jan. 23, when Assembly Democrats, joined by Assemblyman Paul Horcher (I-Diamond Bar), formerly a Republican, expelled Mountjoy on a 40-39 vote. Mountjoy had been holding on to his Assembly seat despite having won a spot in the Senate so that he could continue to play a role in the speakership battle.

With Mountjoy in the Assembly, Brown and Republican Leader Jim Brulte of Rancho Cucamonga were deadlocked, each with 40 votes for the speakership. Once Mountjoy was gone, Brown was able to retain the job by one vote.

Mountjoy immediately took his Senate seat, which he won in a November special election. Former Republican Sen. Frank Hill vacated the seat after he was convicted of political corruption.

Even if a Republican wins the 59th District seat, the balance of power in the Assembly is not expected to change for the time being.

The Assembly’s Republican Caucus will be in the same predicament if Assemblyman Ross Johnson (R-Fullerton) wins a special election, also scheduled for April 11, to fill the state Senate seat vacated by Orange County Supervisor Marian Bergeson.