Todd Ricketts, a co-owner of the Chicago Cubs and son of TD Ameritrade founder Joe Ricketts, was unable to resolve conflict-of-interest issues in taking the No. 2 job at the department.
Ricketts says in a statement that he is "deeply honored" that Trump nominated him for the post.
During the presidential campaign, Ricketts helped raise at least USD 66 million for outside groups called Future 45 and 45 Committee -- a nod to Trump as the incoming 45th president.
But before helping Trump, Ricketts belonged to a super political action committee that spent more than any other trying to stop Trump from winning the Republican presidential nomination.