Gov. Bruce Rauner has donated $50 million to his presumed 2018 re-election campaign, a gift of unprecedented magnitude and a sign to would-be Democratic foes that the Chicago businessman will be all in in seeking a second term.

The contribution to Rauner's campaign fund, made yesterday, became public in a campaign disclosure with the Illinois State Board of Elections.

"This race begins in earnest," said one top Rauner hand, speaking on a not-for-attribution basis. "We can start tomorrow, next week (or) next year. ... It gives us tactical flexibility."

Rauner spent about $50 million backing legislative and other state candidates this year, and spent more than $40 million to win office in 2014. Still, that giving came in the year of an election, not nearly two years in advance, like today's gift.

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Among well-heeled Democrats pondering running against Rauner are hotel scion and investor J.B. Pritzker and former Merchandise Mart operator Chris Kennedy.

Rauner aides declined to comment for the record, but the governor and his wife, Diana Rauner, certainly can afford the gift. Rauner originally made his fortune in the private-equity business and apparently has invested the proceeds well, reporting $188 million in taxable income for 2015.

The early money will allow Rauner to begin defining his potential Democratic foes even before they formally declare, with TV ads and the like, should he so choose. It also will allow him to retain staff and keep a wide range of political operatives working on his behalf, aides who had been brought on for this year's elections.

“Consider this a first installment,” says my background Rauner source. “Our early definition of possible opponents with opposition (material) any second-grader can get off the internet is part one of our standard playbook. We haven't even reached into the good stuff yet.”