The Primary 'Bounce'

John Carey knew all about the problems associated with primary elections: They produce winners who are more partisan than Americans in general, because they require candidates to appeal to partisan primary voters. And when primaries are long and hard -- for example, the marathon struggle between Sens. Barack Obama (D-Ill.) and Hillary Rodham Clinton (D-N.Y.) -- they run the risk of leaving winners so depleted that they can end up losing in general elections.

It came as something of a shock, therefore, when Carey tested the conventional wisdom against empirical evidence. Along with colleague John Polga-Hecimovich, the Dartmouth College political scientist studied about 90 elections and 900 candidates in Latin America, where a growing number of political parties have started to elect leaders through open primaries.

Carey found that politicians who won primaries received a "bounce" of three to six percentage points in general elections, compared with politicians who were nominated or selected by party elites -- a margin large enough to spell the difference between electoral defeat and victory.

"It was, frankly, a surprise," Carey said. "The received wisdom was that there are various ways primaries can hurt candidates, but there was not a lot of research on how it can help them."

Besides discovering gifted politicians who might have been passed over by party insiders, Carey thinks primaries give candidates a boost because voters like transparency. The puzzle, he added, is why the primary "bounce" has not prompted more sweeping reform.

Party insiders who do not want to give up the perks of playing kingmaker are undoubtedly a stumbling block. But that will change as opposition parties start finding charismatic candidates through primaries -- and start winning elections.

-- Shankar Vedantam