I wrote about this recently in the context of the extremely unlikely possibility of Newt Gingrich winning the GOP presidential nomination, but it's worth an item of its own: there's an excellent chance that the current cycle will mark the end of at least one significant nomination streak.
Beginning in 1988, every presidential nominee has had one thing in common -- they've all been employed as elected officials. That's two sitting VPs, four Senators, and three governors. (Yes, Bob Dole was technically out of work for the fall campaign, but he was in office when he captured the nomination).
Before that, however, three consecutive (out-party) nominees were out-of-office pols (ex-governors Carter and Reagan, and former VP Mondale). And the conventional wisdom was that it was a significant advantage to be unemployed, the better to have the time to meet every single voter in Iowa and New Hampshire in the three years leading up to the caucuses and primaries there.
This time, however, it sure looks as if the streak will be broken. Trying to list candidates during the invisible primary stage is always messy, but for now I'll start with two lists published today by Washington insider journalists. Of the leading active candidates listed by Mike Allen and First Read, only Haley Barbour [SEE UPDATE BELOW] currently holds electoral office -- Mitt Romney, Tim Pawlenty, and longshot/joke candidates Jon Huntsman, Rick Santorum, and Newt Gingirch are all out of office. First Read also lists a next tier of possibly active candidates; of those potentially serious contender Mitch Daniels and potentially extremely amusing sideshow Michele Bachmann are current office-holders, while plausible nominee Mike Huckabee and whatever Sarah Palin counts as are not. Might as well finish off the list...on the employed side, Chris Christie gets a mention from First Read, while Ron Paul, Jim DeMint, and Rick Perry do not. Out of office? First Read mentions a few others there, but the only one who is a plausible nominee is Jeb Bush, and unlike the others mentioned in this paragraph he really doesn't appear to running any kind of campaign at all.
So of those who I think have a relatively decent chance of winning, only Barbour, Daniels, DeMint, and Perry would keep the streak alive, with Paul and Bachmann the only others even on the horizon. For what it's worth, the combined Intrade chances of the currently employed total around 25%. That actually seems a bit low to me -- if I were to get into that market, I'd be buying DeMint and Perry -- but at any rate, it does look as if the streak is very likely to end.
[Update: Josh Putnam points out more kindly than I deserve that I totally forgot that Barbour's term expires in January 2012, so he'll be a former office holder during the primaries, caucuses, and general election. So it's even less likely that a currently serving politician will win the GOP nomination]