Illinois Statutes Chapter 10. Elections § 5/25-7. Representatives in congress

§ 25-7. (a) When any vacancy shall occur in the office of representative in congress from this state more than 240 days before the next general election, the Governor shall issue a writ of election within 5 days after the occurrence of that vacancy to the county clerks of the several counties in the district where the vacancy exists, appointing a day within 180 days of issuance of the writ to hold a special election to fill such vacancy.

(b) Except as provided in this subsection (b), the provisions of Article 7 of this Code are applicable to petitions for the special primary election and special election. Petitions for nomination in accordance with Article 7 shall be filed in the principal office of the State Board of Elections not more than 85 and not less than 82 days prior to the date of the special primary election, excluding Saturday and Sunday. Petitions for the nomination of independent candidates and candidates of new political parties shall be filed in the principal office of the State Board of Elections not more than 93 and not less than 90 days prior to the date of the special election, excluding Saturday and Sunday.

Except as provided in this subsection, the State Board of Elections shall have authority to establish, in conjunction with the impacted election authorities, an election calendar for the special election and special primary.