Big news today: Nate Silver and his wonderblog, FiveThirtyEight, are moving on up to The New York Times. Later this summer — probably in early August — FTE’s statistictastic posts will be found in the politics section of nytimes.com.

So, yes, blogger-gone-mainstream, in the manner of an Ezra Klein or, at the Times, a Brian Stelter. Except there’s a key difference between the bought-up-blogger phenomenon and Silver’s arrangement with the Times: The paper hasn’t hired Silver, per se. Rather, it’s licensed FiveThirtyEight, the blog — and only temporarily. As Silver put it in a post announcing the acquisition earlier today, “The partnership agreement, which is structured as a license, has a term of three years.”

That agreement makes the terms of deal, even beyond the acquisition itself, a noteworthy thing in a world of ascendant bloggers and portable brands. (The Freakonomics blog, which moved to the Times in 2007 under a similar brand-licensing arrangement, is the clearest analog we could think of, although Andrew Sullivan’s peripatetic blogging also comes to mind.) As Jim Roberts, the Times’s digital news editor, puts it: “It is unusual — there’s no question. Certainly, for the newsroom, I can’t think of anything like it.”

And that makes the negotiations involved in the partnership — those that have already occurred, and those still to come, as FiveThirtyEight integrates into the NYT and vice versa — both tricky and, at the same time, rather fascinating. When two brands plan to marry, who determines the rules of engagement?

On the one hand, “the fact that it’s a licensing agreement reflects the fact that, in the long run, we retain flexibility,” Silver told me. “And in the short run we retain a certain amount of control over voice and the type of content and material that we cover.”

At the same time, though, “I don’t want to convey the impression that we won’t be subject to New York Times editorial standards. It will be different in the sense that their philosophy is that everything that goes up on their website has to be read by another set of eyes — and I don’t count as that set of eyes.”

As Roberts told me: “We are an edited news organization, and so Nate will be edited — and his contributors will be edited, as well.” The details of that are still being worked out, but “it’s not like we’re just pulling this thing over and letting it run. It will be integrated into our political website, it will be integrated into our political voice, and [Silver] will be working with editors on the national desk and our Washington bureau and political operation.”

And the integration will work both ways. “I also think that we can help him take his blog to a new level,” Roberts says. “There’s a real startup quality to FiveThirtyEight. And we’ve got a giant infrastructure here of graphics editors, multimedia producers, interactive technologists — a lot of people who are big fans of Nate Silver and FiveThirtyEight, who are really eager to work with him. They’ll make his blog better — and I hope we can incorporate some of his insights in different ways in other parts of the website.”

Furthermore, “it’s significant that we’re organized under News rather than Opinion,” Silver points out. That implies, he says, “that there’s going to be more rather than less integration in terms of the overall voice of what the Times is saying. Rather than being “an island within The New York Times,” Silver says, “I think it’s going to be one of the many stations that people pass through as they commute around the site.”

The partnership, as any good one will, should benefit both parties. FiveThirtyEight has “a devoted following of people who I think are kind of like-minded in terms of their interest in our reporting,” Roberts points out. For Silver’s part, he gets the broad readership of the Times — and prime real estate under the banner of the nation’s paper of record. The three-year term of the arrangement will allow FiveThirtyEight to cover the upcoming elections of 2010 — they’re currently building a model to forecast House seats and a refresher version for the Senate, Silver says — and 2012. In the meantime, it will also allow Silver to apply his model-driven approach to sports, pop culture, and other arenas. (His post on KFC’s delightfully disgusting Double Down sandwich is FiveThirtyEight’s most-read post of all time, Silver told me, followed closely by one on marijuana legalization.) “So I think you might see a different version of the website in 2011 than you do in 2010,” he says. Ultimately, “I think we’ll continue to surprise people and evolve around a number of different dimensions.”

The partnership began ten weeks ago, when Silver and Times magazine editor Gerry Marzorati ran into each other on an Amtrak platform in Boston; the initial idea was that Silver would write some pieces for the magazine.

“Within the course of a couple of days,” though, says Roberts, “we were thinking much bigger. I don’t know if we knew at that moment that [incorporating FiveThirtyEight] would be the outcome — but…when we met him and saw that there were just some natural fits, it felt really good.”

Still, “it really took a lot of time to hammer this out,” Silver notes. The Times wasn’t his only suitor; there were other offers from other outlets. “It wasn’t an auction; it wasn’t all about the money, or anything like that,” he says. “We had interest from different people, who represent very different kinds of propositions as far as what they think about media.” Though he won’t go into detail, he notes that “the offers were also very different — not just in a quantitative sense, but a qualitative one. So it just took a lot of time to sort through.”

And: “It was a competitive situation up until the very end.”

Now that the deal’s been done, though, the partnership can really begin. “I know they’re excited, and I’m really excited,” Silver says. “So now we get to do the fun stuff: start to work on the design of the blog instead of working out the contractual deals.”

[Image of Nate Silver via jdlasica under a Creative Commons license]