CHICAGO — The single biggest spender in Republican politics pumped more than $28 million into the GOP in 2021 — and he’s expected to multiply that number leading into the midterms.

Ken Griffin, the founder and CEO of the hedge fund Citadel, was the largest individual donor last year to the GOP super PACs aiming to flip control of Congress, contributing $11 million to the Congressional Leadership Fund and $5 million to Senate Leadership Fund. He splashed another $5 million apiece into Florida Gov. Ron DeSantis’ PAC and into Honor Pennsylvania, a super PAC backing fellow hedge funder Dave McCormick — and opposing celebrity physician Mehmet Oz — in Pennsylvania’s GOP Senate primary, making Griffin the biggest individual donor to those two groups so far.

And yet Griffin hasn’t cut a check so far on what’s likely to be his biggest project of the 2022 midterms: trying to oust Illinois Gov. JB Pritzker. The Chicago-based investor’s years-long feud with his Democratic governor — a fellow billionaire, who just gave $90 million to his own reelection effort and Democratic operations in the state — could turn that gubernatorial race into one of the nation’s most expensive campaigns.