More evidence that contested primaries help

I've long sang the praises of the contested primary, most recently last week when North Carolina's Kay Hagan saw a boost against Dole after winning her primary.

Now, if you listen to the Beltway conventional wisdom, contested primaries are terrible, terrible things. The parties work feverishly to "clear the field" for favored candidates, forcing out less-attractive primary opponents regardless of how many feathers are ruffled at the grassroots level. Party officials would prefer that candidates spend time raising money rather than spending it, especially if the opposing party has cleared its own field.

Yet a bitterly contested primary wasn’t a terrible thing for over half of the Senate’s newest members. Ten of the 19 senators first elected in 2004 and 2006 triumphed in contested primaries before defeating general election opponents who had been "blessed" with cleared primary fields.

In 2004, that list included Republicans Tom Coburn in Oklahoma, Jim DeMint in South Carolina, Richard Burr in North Carolina and Lisa Murkowski in Alaska, as well as Democrat Barack Obama in Illinois. In 2006, that list included Democrats Jon Tester in Montana, Jim Webb in Virginia, Bob Casey Jr. in Pennsylvania and Ben Cardin in Maryland, as well as Republican Bob Corker in Tennessee.

I went back to see if Webb's victory in 2006 was mostly influenced by Macaca, or whether his primary victory played a role. Here's Rasmussen polling of the race for the year:

       Allen  Webb

Feb 8    49    37
Mar 15   54    30
Apr 11   50    30

June 13, Webb wins his primary

Jun 14   51    41
Jul 18   50    39

August 11: Macaca

Aug 16   47    42
Sep 12   50    43
Oct 1    49    43
Oct 12   47    44
Oct 24   49    48
Oct 29   46    51

Final results: Webb 50, Allen 49

Webb's primary victory was immediately worth about a 10-point boost, a boost he never relinquished. Macaca was worth another six points or so, and put him close enough to close the deal the final weeks of the race.

But it's clear, given the numbers, that the single biggest boost for his campaign was winning his primary.