Constitution of the State of Illinois Art. V, § 6. Gubernatorial Succession

(a) In the event of a vacancy, the order of succession to the office of Governor or to the position of Acting Governor shall be the Lieutenant Governor, the elected Attorney General, the elected Secretary of State, and then as provided by law.

(b) If the Governor is unable to serve because of death, conviction on impeachment, failure to qualify, resignation or other disability, the office of Governor shall be filled by the officer next in line of succession for the remainder of the term or until the disability is removed.

(c) Whenever the Governor determines that he may be seriously impeded in the exercise of his powers, he shall so notify the Secretary of State and the officer next in line of succession. The latter shall thereafter become Acting Governor with the duties and powers of Governor. When the Governor is prepared to resume office, he shall do so by notifying the Secretary of State and the Acting Governor.

(d) The General Assembly by law shall specify by whom and by what procedures the ability of the Governor to serve or to resume office may be questioned and determined. The Supreme Court shall have original and exclusive jurisdiction to review such a law and any such determination and, in the absence of such a law, shall make the determination under such rules as it may adopt.