Note to Prez Hopefuls: Quit Your Day Job

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Here's a political truism: When it comes to running for president, it's best to be unemployed. Or at least work a day job with a lot of free time, like governor or vice president.

Truth is, it's hard out there for a senator running for president. Washington trivia nerds like to point out that John F. Kennedy was the last sitting senator elected president. There are any number of explanations for this, not the least of which is that senators have voting records. But two tight votes in the Senate this week, where two Republicans banded together with 48 Democrats to support a troop-withdrawal provision in a military spending bill, underscored another reason: They have to be in Washington three days a week.

Monday's 50-48 vote was the seventh time this year that a measure has come within a two-person margin of passing or failing, by our analysis. List of all 2007 roll call votes here.

(Note: Some votes appear to be very close, but actually required 60 votes to pass.) This is bad news for the six current senators running for president. With the distinct possibility that one or two missing senators could spell the difference between victory or defeat, they will have a much harder time skipping out of Washington during the week. Four of the six would-be presidents in the Senate are Democrats, putting the majority party at a larger disadvantage in keeping the reigns on four members -- Joe Biden, Hillary Clinton, Chris Dodd, and Barack Obama -- who would probably rather be feasting on barbeque with union guys in Sioux City. With a one-seat majority and one of their number, Tim Johnson of South Dakota, recovering from brain surgery--plus Independent Joe Lieberman becoming increasingly unmoored from the party over Iraq--every vote counts. The Republicans are equally reliant on Sam Brownback and John McCain.

In the past, when one party held a comfortable majority, senators making a go for the presidency could afford to put their legislative duties on hold. According to Congressional Quarterly's vote participation study, then presidential hopeful Sen. John Kerry cast a ballot on 36 percent of Senate votes in 2003 and only 10 percent in 2004.

Ironically, this may have hurt his campaign. Once he had won the nomination, Kerry was frequently described by opponents as "the most liberal member of the Senate," based on a similar vote study by National Journal, which determines which votes are a test of party loyalty and calculates each lawmaker’s adherence to the partisan dogma. As an aide in Dodd's campaign pointed out to News Desk, Kerry's extremely liberal score probably had a lot to do with the fact that he showed up for only the most important votes.

Spokespersons for various senators running for president tend to start with platitudes about their candidate's loyalty to his or her day job. But privately, they acknowledge that it's hard out there for a senator, particularly ones without the cash on hand to charter private jets.

This gives unemployed candidates like John Edwards and Mitt Romney an edge (though both are still in third place right now in the polls). But even once the field is narrowed to the final two candidates, a senator on the campaign trail could spell trouble for party leaders in Washington.

In other words, any senator still in the race next year may need to show up to work more than 10 percent of the time.

--Chris Wilson