Under party rules, Democratic and Republican ward leaders whose territories include parts of each legislative district will meet in coming days to choose their respective party candidates for the special elections.
Those two candidates will face each other on the April 24 ballots, with the winner to serve the remaining seven months of the term, through the end of this year.
Meanwhile, larger groups of candidates - as many as seven Democrats vying for the Williams seat, and six Democrats going for the Johnson seat - will appear on primary ballots seeking party nominations for the two-year legislative term beginning next January.
Those contests will be decided by voters, not the ward leaders, and the primary election winners will face each other in November.
The Supreme Court was divided 4-3 on whether to compel state House Speaker Sam Smith to schedule the special elections for April 24. Smith contended he was legally obliged to wait until a Legislative Reapportionment Commission comes up with new boundaries based on the 2010 census results.
But the court held that the state constitution requires the seats to be filled more quickly. Justices were divided along partisan lines - the three Democrats, whose party stands to gain seats in four heavily Democratic districts - voted to force the election. Three Republicans dissented.
Chief Justice Ronald Castille broke with his GOP brethren to decide the issue, just as he did in the majority decision in January that threw out the commission's first redistricting map.
Contact Bob Warner at 215-854-5885 or firstname.lastname@example.org.