Early on, Roosevelt was quite adept at bargaining with corporations. In his first 100 days, to attract corporate support for the National Industrial Recovery Act, he won collective bargaining, minimum wages and maximum hours in exchange for a temporary suspension of antitrust law, so businesses could fix prices. To establish the Securities and Exchange Commission in 1934, he made concessions to Wall Street that scrapped statutory requirements in favor of regulatory flexibility. The following year, to allow the Federal Reserve to better conduct monetary policy, he gave bankers representation on the policy committee.

Johnson also found little value in warring with corporations. He won a Keynesian tax cut in early 1964, defeating budget-conscious conservatives, thanks to a broad coalition that included corporations. He attracted business support to back his first antipoverty bill by junking plans to promote family farming and push businesses to hire long-term unemployed people. He created the Transportation Department, in 1966, only after exempting resistant shipping interests from its jurisdiction. He incited a new era of environmental protection, increasing federal responsibility for cleaning air and water, while defusing corporate opposition by trading away federal pollution standards.

Democratic presidents typically pay dearly when they choose to fight corporations instead of deal with them. Jimmy Carter sapped his political capital in the first two years of his presidency by trying to pass, with belligerent anticorporate rhetoric, a National Energy Act that would reduce our dependence on oil. He gave two major national addresses intended to rally the public and fend off critics’ attacks. At a town hall, he lashed out at oil companies for enjoying “a position of privilege in our country for too long” and having undue influence in Congress. But these confrontational tactics failed to rouse enough public ire to trump that influence, and Mr. Carter settled for a far smaller energy bill than he originally demanded.

Or consider President Bill Clinton. In 1993, his health care task force largely resisted meeting with insurance lobbyists as it drafted legislation. In turn, the insurers didn’t wait for the legislation to be finalized before embarking on a vicious advertising campaign. When the first lady, Hillary Rodham Clinton, tried to belittle that effort, fund-raising for the insurance lobby skyrocketed and its advertising budget quintupled. Mr. Clinton, his bully pulpit diminished, couldn’t get Congress to vote on his bill. He suffered such a humiliating defeat that his ability to enact any other progressive reform was severely crippled.

The realities of corporate power cannot be wished away by any president, no matter how tough the talk, because corporations can and will spend freely during the legislative process. And when they are unified, they have the resources to dominate debate. Even the progressive holy grail — a constitutional amendment banning corporate campaign donations — would not stop that.