The commencement of proceedings in the case of contests of the second, third, fourth and fifth classes shall be by petition, which shall be made and filed, as herein required, within twenty days after the day of the primary or election, as the case may be. The petition shall concisely set forth the cause of complaint, showing wherein it is claimed that the primary or election is illegal, and after filing may be amended with leave of court, so as to include additional specifications of complaint. After any such amendment, a reasonable time shall be given to the other party to answer.
25 P.S. § 3456