John McCain has a lengthy history of being a budget hawk, and one of his bugaboos has been earmarks. One of the reasons the GOP establishment dislikes McCain is that he has been very forthright about calling his fellow Republicans out for earmarking pork-barrel giveaways — as much as he was when Democrats ran the Congress.
Barack Obama and Hillary Clinton both have some earmarking of their own to account for; however, they apparently couldn’t find any reason not to oppose earmarking themselves and therefore have both agreed to cosponsor the DeMint-McCain anti-earmarking bill. (At least, according to Glenn Reynolds, they have.)
This is a good thing, and it is good politics for McCain. First, if Clinton or Obama do earmark anything from now on, they look like hypocrites. And at least one of them needs to remember that they’ll be going back to the Senate and not on to the White House, so the temptation to earmark will be great.
Second, they now get to be asked questions about any past earmarks they’ve made. (So does McCain, but he’s pretty clean on this point.) That generates an additional campaign issue for McCain, and helps frame his candidacy as one of fiscal responsibility.
Third, Jim DeMint is really, really conservative, and highlighting McCain working hand-in-glove with him helps shore up McCain’s vulnerable right flank.
Fourth, and most importantly, it shows that McCain is the leader and Clinton and Obama are following him. They’ll call it “bipartisanship” instead, but the fact of the matter is that everyone knows they wouldn’t have even agreed to the proposal, much less co-sponsored it, if they weren’t running for President and in need of offering some sort of way to promise to fix the budget deficit. That they could only come up with an idea that McCain has been pushing for years shows that McCain is not only leading the country, he’s even leading his opponents.