If you need something out of Washington and want to give a satchel of cash to a political candidate, no need to give it directly to the candidate. Federal law limits those contributions to $2,600 anyway. The thing to do is to give the money to the candidate’s “super PAC,” where no limits apply, to pay for attack ads against the candidate’s opponent.

That’s the path chosen by John Childs, a private-equity investor, who gave $250,000 to Senator Mitch McConnell’s super PAC, Kentuckians for Strong Leadership. (Could it have anything to do with Mr. McConnell’s staunch opposition to a tax increase on hedge fund managers, favored by President Obama and Democrats?) Joseph Craft, a billionaire coal executive, gave $100,000, and Donald Trump gave $50,000 to the same group.

Naturally, Mr. McConnell’s Democratic opponent in the Kentucky Senate race, Alison Lundergan Grimes, set up her own super PAC, We Are Kentucky, to attract money from those on the left who would love to oust the Senate minority leader. The United Auto Workers gave it $100,000, as did the big plumbing and pipe-fitting union.

This election year will be the moment when individual candidate super PACs — a form of legalized bribery — become a truly toxic force in American politics. The giant ideological super PACs formed by political operatives like Karl Rove spent hundreds of millions in 2012, but didn’t produce the conservative revolution demanded by the big donors. So now the torrent of cash is heading toward smaller groups set up to promote a single candidate or, more often, to trash that candidate’s opponent.