On Sunday, during an appearance on "This Week with George Stephanopoulos", Nate Silver said something entirely uncontroversial. He predicted that, as of today, his modeling showed Republicans winning the six seats they need to regain the Senate majority this fall.

We think the Republicans are now slight favorites to win at least six seats and capture the chamber. The Democrats’ position has deteriorated somewhat since last summer, with President Obama’s approval ratings down to 42 or 43 percent from an average of about 45 percent before. Furthermore, as compared with 2010 or 2012, the GOP has done a better job of recruiting credible candidates, with some exceptions.

That's nothing different than what independent political handicappers like Stu Rothenberg and Charlie Cook have been saying for the last month or so. Heck, even the Fix was onto the Republican momentum by last Monday.

But, Silver's prediction was greeted with significantly more hand-wringing -- and pushback -- than any of the pronouncements by the likes of Rothenberg and Cook. Guy Cecil, the executive director of the Democratic Senatorial Campaign Committee, penned a memo Monday morning arguing that while Silver is a smart dude, his model isn't always infallible. Wrote Cecil:

Nate Silver and the staff at FiveThirtyEight are doing groundbreaking work, but, as they have noted, they have to base their forecasts on a scarce supply of public polls.  In some cases more than half of these polls come from GOP polling outfits. This was one reason why FiveThirtyEight forecasts in North Dakota and Montana were so far off in 2012. In fact, in August of 2012 Silver forecasted a 61% likelihood that Republicans would pick up enough seats to claim the majority. Three months later Democrats went on to win 55 seats.

Why the sturm und drang surrounding Silver's predictions?  A few reasons.

1.  Silver is a modeler, meaning that he has created an equation -- weighing polls, past performance in state and by candidates etc. -- that spits out a percentage likelihood of a seat changing parties. (Our own Monkey Cage Blog has a 2014 election model of their own.) Numbers = certainty for many casual observers of politics. And so, despite Nate's warning about the danger of putting all your eggs in the model's basket at this point in the election, lots and lots of people do exactly that. If Nate says there is a 78 percent chance of something happening, well then there is a 78 percent chance of something happening. That's a different thing than what Cook/Rothenberg do;  neither are modelers, relying instead on reporting and collected wisdom about how campaigns run (and win/lose) to produce rankings like "toss up", "lean Democratic" and "solid Republican." There's far less of an air of certainty in those ratings than in the number Silver produces.

2. Silver's appeal and influence has reached well beyond the Beltway and political junkie communities. During the 2012 election, Nate was harvesting vast amounts of traffic for his prognostications on the New York Times Web site. In that election, he became a brand that stood outside of the influential but relatively circumscribed world of politics -- a status affirmed by his move after the election to re-imagine fivethirtyeight.com with ESPN.  When he makes predictions, he has the potential to drive news cycles and influence coverage across the country.

3. Know who REALLY listens to what Nate says? Major Democratic donors. They follow his projections extremely closely and, if he says the Senate majority won't be held, they take it as the gospel truth. That, of course, is a major problem for the DSCC and other Democrats focused on keeping control of the Senate -- particularly given that major outside conservative groups led by Americans for Prosperity are already spending heavily on ads bashing vulnerable Democratic incumbents. If the major donor community concludes that spending on the Senate isn't a worthy investment, Cecil and his Democratic colleagues know that their chances of holding the majority get very, very slim. Nate's predictions move money in Democratic circles. Cecil knows that. Hence the memo.