Occasionally you’ll hear chuckling from Democrats that rise of the Tea Parties has greatly complicated the electoral outlook for the Republican Party, as its moderate incumbents will face costly primary challenges and be left more vulnerable for the general election. On paper, that could happen in someplace like Indiana, where challenger Richard Mourdock would not have all of the advantages of incumbency that Sen. Richard Lugar enjoys. But Indiana’s still a pretty conservative state, with Obama’s by-the-skin-of-his-teeth victory in 2008 unlikely to be duplicated, and so it’s hard to call Democrat Joe Donnelly much of a favorite, at least so far. Then there’s this inconvenient fact:

The conventional wisdom surround Congressman Joe Donnelly’s entry this week into race for U.S. Senate is that Mourdock has a good chance of defeating Sen. Richard Lugar in a primary and Democrats match up well against Mourdock in the general election.  That confidence is not supported by arithmetic.  In the 2010 general election, Richard Mourdock defeated Joe Donnelly in the second district by 21,000 votes.  It’s worth noting that Mourdock’s Democrat opponent was Pete Buttigieg, who is from the 2nd District and the next mayor of South Bend.

Beyond Indiana, there aren’t a lot of races where the Tea Party challengers are likely to prompt the defeat of GOP incumbents, at least in Senate races. For example, in Maine, Olympia Snowe would seem to fit this scenario, as she’ll face primary challenges from Andrew Ian Dodge and Scott D’Amboise. Except a Democrat takeover traditionally requires an actual Democratic candidate, and
so far, no member of the party has filed papers to take on Snowe.

Then there’s Scott Brown in Massachusetts, who is likely to have a tough campaign in heavily-Democratic Massachusetts in 2012, but who has, at least at this point, no GOP primary challenger. He also announced today that he is sitting on $9.6 million in cash-on-hand, a nice advantage.

Also lacking any announced primary challengers at this point is Sen. Orrin Hatch of Utah. Of course, considering the voters of that state, the chances of a Democrat pickup are slim.

Mississippi? No, so far Democrats are still looking for someone to run against Roger Wicker.

Of course, it’s relatively early in the cycle, and additional challengers can throw their hats in the ring. But the hesitation in some races, where one might have expected enthusiastic challengers, knocks down the conventional wisdom…