IL provides that if no one runs in the primary from an established party, the county party leaders can slate a candidate to fill the ballot vacancy. Many candidates run this way, particularly against incumbents.
Do the different county leaders in a multi-county district have to agree? Can different county leaders choose a different candidate?
The county leaders have a weighted vote based on the number of ballots for their party taken in the most recent primary in that district. The form to slate the candidate must be signed by leaders with over half the weighted vote.
Has any such candidate ever won?
About 30 to 50 candidates go on the ballot this way for state legislative and congressional seats each cycle. None have won this decade. I don't have data for older races, nor for county board races.