The biggest beneficiaries of increased viewership are the also-rans. The debates keep them in the race. At no cost, they get the attention of millions more voters than they ever could on their own. And the debates put them on equal footing with candidates who are well-financed and better organized. The marginal candidates have no incentive to drop out.

Once the also-rans sign up for a debate, the stronger candidates are all but required to show up, if only to avoid the embarrassment of being represented before a national audience by an empty chair. The also-rans and the cable people have them over a barrel.

For Republicans, a campaign dominated by televised debates has two disadvantages. It puts the folks they loathe, the press, in control. The media can dwell on subjects such as tax cuts for the rich or social issues that one or more of the candidates would prefer not to discuss. They are hard pressed to squeeze their talking points into the dialogue. Mr. Obama gets a pass.

Since the media pit the candidates against each other, Mr. Obama’s strategists get an early glimpse of the vulnerabilities of the Republican candidates, their strengths and weaknesses on issues, and the attacks used most effectively against them. All Mr. Obama has to do is sit back and enjoy the show.