Unlike Palin, most campaign managers and party chairmen hate primaries. They hate to see money spent fighting people on the same team, and they fear the scars that may be left.

But Palin has a strong point, especially when a party has as many unsettled issues as the Republicans do these days. In such a situation, primaries are the best way to test leaders and ideas. The modern Republican Party began recovering from the many defeats of the New Deal era only in 1952, when Dwight Eisenhower, a war hero, defeated Adlai Stevenson. But before Ike could win the general election, he had to face down Robert A. Taft, the leader of the GOP congressional wing and an embodiment of conservatism. Their battle started in the New Hampshire primary and continued through bitter convention roll calls testing and finally overthrowing establishment control.

Another such fight came in 1980, after the ruin of Watergate had restored Democrats to the White House. Ronald Reagan and George H.W. Bush squared off, with Bush winning the first round in Iowa, and Reagan forced to defend his claim in New Hampshire and in later primaries. Without those tests, Reagan would not have been the candidate who ousted Jimmy Carter.