May 9, 2007

The Lugar-Mourdock Race:
A Test of the ‘Divisive Effect’?

For release May 2 and thereafter (645 words)

by Andrea Neal

If family feuds make you squirm, you’ll be glad when this primary’s over. While Democrats across Indiana have lain low, infighting among Republicans has rivaled that of Cain and Abel.

Dick Lugar — “Obama’s favorite Republican.”

“Treasurer Richard Mourdock’s got problems.”

“We can’t trust David McIntosh as our congressman.” Etc., etc.

In close primary races, such as the Lugar-Mourdock battle, and with an open House seat at stake, as in the heavily Republican 5th District, the heated rhetoric is no surprise. The concern for Republicans is that they will end up self-destructing. Aren’t they handing Democrats on a silver platter some of the most potent arguments to be used against them in the fall?

Nobody knows.

Conventional wisdom holds that there’s a “divisive primary effect.” The bloodier a primary, the less likely the winner will prevail in the general election.

The theory is based on several assumptions: 1. That the candidate will emerge so bruised from the primary that he can’t recover. 2. That followers of the losing candidate will not wholeheartedly support their party’s nominee, and 3. That to win a divisive primary a candidate must cater to a more extreme wing of the party, which will hurt him/her in the November election when voters value moderation.

Pundits have been championing this theory for decades, yet it’s been studied by dozens of political scientists, and they’ve all reached different conclusions.

A 2005 article in Legislative Studies Quarterly noted, “Some studies have found that divisive primaries hurt candidates in the general election; others have found a mixed relationship or none at all. Recent scholarship has even begun to turn the common wisdom on its head, finding that divisive primaries actually help U.S. House challengers.”

The 2008 primary between Barack Obama and Hillary Clinton provided another case study. Republican John McCain clinched the GOP nomination by early March; Democrats battled until June when Clinton finally conceded there was no way for her to win the delegate count at the Democratic National Convention.

One researcher found that Obama’s general election vote totals were higher in the most competitive primary states. Another concluded that the divisive primary suppressed turnout among some voters and caused more defections to John McCain and the Republicans. Either way, Obama won the popular vote with a whopping six-point margin.

Although it’s dated, a major 1984 study by Patrick Kenney and Tom Rice examined the relationship between primary divisiveness and general election results in gubernatorial and senatorial elections. Its conclusion: “A divisive primary adversely affects a party’s chance for general election victory.” Curiously, the study found that divisive primaries hurt Senate candidates more than governor candidates and Democrats more than Republicans. Subsequent studies have challenged these findings.

Equally curious, when it comes to state legislative races, the divisive primary effect does not seem to apply. Researchers analyzed legislative campaigns in nine states during the 1994 and 1996 election cycles. “Greater divisiveness in a candidate’s primary leads to a higher vote share in the general election. Similarly, greater divisiveness in a general election opponent’s primary leads to a candidate receiving a lower vote share. Simply the presence of a primary challenge is found to exert a substantial positive influence for a candidate in the general election, particularly in open seat contests.”

Of course, in heavily partisan districts, the divisive primary effect is irrelevant. The eight-way Republican primary battle to replace retiring 15-term Rep. Dan Burton is so heated because it will determine the general election winner. Democrats don’t stand a chance in the 5th District.

The Lugar-Mourdock primary is a different matter. A Howey-DePauw Indiana Battleground Poll indicates Lugar would trounce the lesser-known Democratic contender, Joe Donnelly, while Mourdock and Donnelly are tied at 35 percent.

The outcome of this family feud will not only provide fodder for political scientists studying the divisive primary effect, it could have disastrous consequences for Republicans come November.

Andrea Neal is adjunct scholar with the Indiana Policy Review Foundation. Contact her at


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