How often has John McCain been away from the Senate? Well, let's put it this way: At this point, he has missed more votes than even South Dakota Democrat Tim Johnson, who couldn't work for almost a year after suffering a brain hemorrhage in late 2006.

I see today, from Think Progress, that McCain took over the dubious distinction of being the Senate's most absent member in April of this year, and that CQ Politics says he hasn't voted since April 8.

According to the Washington Post, McCain has missed 367 votes during the 110th Congress, 61.4 percent of those held. Johnson has missed 311 votes, 52 percent of the total. In third place is Barack Obama, who has missed 259 votes -- 43.3 percent. Not surprisingly, the next four most absent senators (Hillary Clinton, Joe Biden, Chris Dodd and Sam Brownback) also ran for president this year.

CQ Politics notes that both Obama and McCain are likely to keep missing a fair number of votes, both because of scheduling conflicts and for political reasons. It's easier to avoid getting attacked on an issue if you didn't actually vote on it. That way, you can tailor your position in a way that might be more politically acceptable than the actual bill was. Because of this, Obama will probably continue to miss fewer votes than McCain -- Democrats control the Senate's agenda and can protect Obama from having to vote on potentially controversial legislation.

In a similar situation in 1996, when he was challenging then President Bill Clinton, former Sen. Bob Dole resigned from his seat. McCain has said that, for the moment, he has no plans to do the same. (John Kerry, obviously, kept his seat when he ran for president in 2004.)