AFTER John McCain discovered that his campaign was nearly broke — at a time when he was already hemorrhaging in public opinion polls — he did what presidential candidates in trouble always seem to do: he forced out his top consultants....

Nelson Warfield, a media consultant advising Fred Thompson, a likely Republican presidential candidate, said: “How are important are they? I think in a presidential race there are larger dynamics at work than some guy can fix by telling you how to part your hair.”Consultants have been around presidential candidates almost as long as there have been presidential candidates. But as news coverage of campaigns moved from the public stage to internal workings — scrutiny encouraged by behind-the-scenes books like “The Selling of the President” by Joe McGinniss about the 1968 race — operatives increasingly found themselves sharing a moment on the evening news with the candidate.

The first glimmers of this era came with Patrick Caddell, the colorful South Carolinian pollster who advised Jimmy Carter in 1976. The phenomenon was established when Lee Atwater took a high-profile role in the election of George H. W. Bush in 1988. By 1992, it seemed only natural that a documentary film portrayed the deliberations of James Carville, Paul Begala and George Stephanopoulos as they helped elect Bill Clinton.