Ok, I should know better than to reply to total asshats, but just because I was looking up Silver:
2010 U.S. mid-term electionsShortly after 538 relocated to The New York Times, Silver introduced his prediction models for the 2010 elections to the U.S. Senate, the U.S. House of Representatives, and state Governorships. Each of these models relied initially on a combination of electoral history, demographics, and polling.
[ edit]U.S. SenateStimulated by the surprising win of Massachusetts Republican Scott Brown in the special election in January 2010, Silver launched the first iteration of his Senate prediction model a few days later, using objective indicators including polling to project each state outcome in November. This model incorporated some elements of the 2008 presidential model. [93] It was first published in full form in The New York Times on August 25, 2010. [94] It relied basically on aggregating of public polls for each Senate race, with some adjustment for national trends in recognition of a correlation in poll movement across state lines, i.e., each race cannot be interpreted as entirely independent of all others.
In addition to making projections of the outcomes of each Senate race, FiveThirtyEight tracked the expected national outcome of the partisan division of the Senate. Just before election day (October 31), the FiveThirtyEight Senate projection was for the new Senate to have 52 Democrats and 48 Republicans. (The model did not address the possibility of party switching by elected candidates after November 2.)
Of the 37 Senate seats contested in the November 2, 2010 elections, 36 were resolved by November 4, including very close outcomes in several states. Of these 36, the FiveThirtyEight model had correctly predicted the winner in 34. One of the two misses was in Colorado, in which the incumbent Michael Bennet (D) outpolled the challenger Ken Buck (R) by less than 1 percentage point. The 538 model had forecast that Buck would win by 1 percentage point. The second miss was in Nevada, in which the incumbent Harry Reid beat challenger Sharron Angle by 5.5 percentage points, whereas the 538 model had forecast Angle to win by 3.0 percentage points. Silver has speculated the error was due at least in part to the fact that polling organizations underrepresented Hispanic voters by not interviewing in Spanish. [95]
In the remaining contest for U.S. Senate, in Alaska, the electoral outcome was not yet determined as of November 4, pending a count of the write-in ballots, but in the end the FiveThirtyEight forecast of GOP nominee Joe Miller as winner ultimately proved to be wrong, as write-in candidate, incumbent Republican Senator Lisa Murkowski, prevailed.
The 538 model had forecast a net pickup of 7 seats by the Republicans in the Senate, but the outcome was a pickup of 6 seats.
[ edit]U.S. House of RepresentativesThe model for projecting the outcome of the House of Representatives was more complicated than those for the Senate and governorships. For one thing, House races are more subject to the force of national trends and events than are the other two. One way to account for this was to take into account trends in the "generic Congressional ballot." [96] Use of such a macrolevel indicator, as well as macroeconomic indicators, is a common approach taken by political scientists to project House elections. [97]
Furthermore, there was much less available public polling for individual House districts than there is for Senate or gubernatorial races. By the end of the 2010 election season, public polls were available for only about 25% of the districts. This is one reason why some analysts rely principally on making global or macro-level projections of the number of seats to be won by each party rather than trying to forecast the outcome in every individual district. Silver'sFiveThirtyEight model, however, while weighting the generic partisan division as one factor, focused on developing estimates for each district. For this purpose he used information on past voting in the district (the Cook PVI), the quality of the candidates (in particular whether one was an incumbent), fundraising by each candidate, "expert ratings" of the races, [98] public polls of the given race (if they were available), and, in the absence of public polls a cautious use of private polls (i.e., polls conducted by or for partisan organizations or a candidate's own campaign organization).
In response to some concerns that he was hedging his projection, Silver contended that in his model the uncertainty of the outcome was a feature, not a flaw. [99] In comparison with previous Congressional elections, a far larger number of seats were being contested or were "in play" in 2010. While his model, which relied on simulating the election outcomes 100,000 times generated a projected "most likely" net gain of 53 seats by the Republicans (two days before the election), he emphasized that the 95% confidence interval was ± 29–30: "Tonight, our forecast shows Republicans gaining 53 seats – the same as in recent days, and exactly the same answer you get if you plug the generic ballot average into the simple formula. Our model also thinks the spread of potential outcomes is exceptionally wide: its 95 percent confidence interval runs from a 23-seat Republican gain to an 81-seat one". [100] [101]
On election eve, he reported his final forecast as follows:
Our forecasting model, which is based on a consensus of indicators including generic ballot polling, polling of local districts, expert forecasts, and fund-raising data, now predicts an average Republican net gain of 54 seats (up one from 53 seats in last night's forecast), and a median net Republican gain of 55 seats. These figures would exceed the 52 seats that Republicans won from Democrats in the 1994 midterms. [102]
In final vote tallys as of December 10, 2010, the Republicans had a net gain of 63 seats in the House, 8 more than the total predicted on election eve though still within the reported confidence interval. [103]
[ edit]State governorshipsThe FiveThirtyEight model for state governors' races also relied basically on aggregating and projecting public polls in each race. However, Silver reported that gubernatorial elections in each state were somewhat more independent of what happened in other states than were either Senate or House of Representatives elections. That is, these races were somewhat more local and less national in focus.
Just before election day (October 31), the FiveThirtyEight projection was that there would be 30 Republican governors in office (counting states where there was no gubernatorial election in 2010), 19 Democratic governors, and 1 (actually 0.8) Other ( Lincoln Chaffee, who was leading in the polls running as an Independent in Rhode Island).
Of the 37 gubernatorial races, FiveThirtyEight correctly predicted the winner of 36. Only in Illinois, in which the Democratic candidate Pat Quinn defeated the Republican Bill Brady 46.6% to 46.1%, was the FiveThirtyEight prediction wrong. en.wikipedia.org |
