Rauner opened a campaign office in the credit union's service area, which made him eligible to join as a member, Brown said.

“I would have done what we've done today irrespective of the campaign,” Rauner told local media after making the deposit.

Brown, who helped launch South Side Community FCU almost 11 years ago and serves on the board of National Federation of Community Development Credit Unions, pointed out that the cooperative is a non-partisan, not-for-profit organization whose mission is to economically empower the community.

The small credit union had to look at the capital versus asset implications of accepting such a large amount.

“A large deposit alone tends to lower our net worth – unless you have an increase in capital,” Brown said. “This way, we are enhancing our net worth and maintaining a healthy capital asset position, while gaining more capacity to help more members.”

There were other challenges involved in receiving such a high-dollar, high-profile deposit and donation, he said.

“One of the biggest challenges will be managing the expectations of members, who might perceive this as a $1 million donation that we're going to give out quickly, but the transaction was primarily a deposit, which we hope will enable us to steadily and strategically grow our loan portfolio,” Brown said.