I'm not sure this will work because of "standing". It may have to be a candidate that gets disqualified.
Not saying this is fact, just a possibility.
Voters have standing.
No they don't. They haven't been deprived of anything. There has to be a candidate disqualified from running because of the law, and that candidate can sue, but voters don't have a case until a client is disqualified from running for office by his/her failure to comply with the law.
Only a crook or a liar would refuse. The request is not unreasonable. What is unreasonable is Trump's refusal to comply with this request.