You can find the unanimous opinion (with one judge not participating) here.

This is the right result under the Democracy Canon. Courts should bend over backwards to make sure that voters have a real choice on election day.

The Court based its ruling on laches (unreasonable delay in filing the lawsuit). This too is correct; in election cases, people should not have an option to see an election violation and then just wait until it is to their advantage to file suit. I make that case in Beyond the Margin of Litigation.