Hillary Clinton is currently in the lead for the Democratic Party presidential nomination, but her odds are getting worse as Bernie Sanders gains on her in the polls according to a computer model designed to predict who will be the nominee. An algorithm designed to weight both the polls and the endorsements received by the major candidates gives Clinton a 62 percent chance of winning the Democratic primary, compared to 38 percent for Bernie Sanders. The last run of this forecast had Clinton with a 68 percent chance to win the nomination, which means her odds have gone down by 6% over the last month. The algorithm takes into account polls released from a variety of sources, including polls released over the last 24 hours from CNN/ORC and KBUR.
The algorithm works by giving a certain weight to a number of factors in calculating the odds that each candidate will eventually win the Democratic Party nomination. The heaviest weight, 30 percent, is given to the New Hampshire primary, which has tended to be the most predictive contest over the last 20 years. Other factors included are polling of the Iowa Caucus (20 percent), South Carolina primary (10 percent), and nationwide polling (20 percent). Finally, to account for the effect of the party establishment and super delegates a 20 percent weight is given to the number of endorsements candidates have received using FiveThirtyEight’s measurement of official endorsements for each candidate.
So what do the polls say?
A Real Clear Politics average of four New Hampshire primary polls now has Sanders with a double-digit lead. Sanders has the lead with 52.0 percent support according to the average of all the polls. Clinton trails Sanders by 12.5 points with 39.5 percent support. Since early December a total of 11 polls have Sanders winning New Hampshire, and five of those polls give Sanders a double-digit lead. As seen below, Sanders is trailing in Iowa and in national polls. If Sanders can win New Hampshire their is a good chance he could carry that momentum into the Super Tuesday primary contests to make for a more competitive race. In 2008 then Senator Obama used victory in New Hampshire to eventually overtake Hillary Clinton in the nationwide polls, and in 2004 New Hampshire helped boost Senator John Kerry to victory.
The Real Clear Politics average of polls in Iowa currently has Clinton as the leader with 46.3 percent support, compared to 43.1 percent for Sanders. As was the case in New Hampshire, Sanders has been gaining on Clinton in Iowa. In December most polls had Clinton with a double-digit lead over Sanders in Iowa, but then two polls in early January actually gave Sanders the lead. Since then Clinton seems to have regained her footing. Of the last five polls released Clinton is winning four. The bottom line is Iowa is now much closer, and if Sanders can win both Iowa and New Hampshire his momentum may be an insurmountable obstacle for the Clinton campaign.
The Real Clear Politics average of nationwide polling is one of the remaining sources of Clinton’s strength. The RCP has Clinton polling at 51.2 percent nationally compared to 38.0 percent for Sanders. It is worth noting, however, that nationwide polls tend to fluctuate wildly in the months before and after the Iowa Caucus. At this point in 2008 most polls had Clinton leading with about 45 percent support nationally over 34 percent support for Obama, but Obama went on to win the nomination. In December of 2004 Howard Dean and Dick Gephardt held the lead nationally and John Kerry was only polling in the low teens.
The biggest factor contributing to Clinton’s lead is her dominant lead in the endorsement race. As documented at FiveThirtyEight.com, citing a study done by four prominent political scientists, significant endorsements from members of the party tend to cause success in primary states. In previous elections the party elites tended to favor one candidate ahead of the Iowa Caucus and New Hampshire primary, and that candidate tended, with few exceptions, to go on to win the party nomination. Using Silver’s measurement of endorsements, which gives more weight to endorsements from U.S. Senators and state governors than U.S. Representatives, Clinton currently dominates the endorsement race with 458 points, compared to just 2 points for Sanders. Historically, a candidate who dominates the endorsement race as Clinton is currently doing goes on to win the party nomination..
As the campaign goes on the polling numbers, particularly those in Iowa in New Hampshire, will take on more weight. The Democratic Primary is currently at a critical stage. Sanders has undoubtedly gained on Clinton and now is a real threat to win the nomination. The question is whether Clinton can reverse that momentum in the coming weeks. Clinton still holds the lead nationally and clearly has the support of the establishment, but all of that could change if Sanders wins Iowa and New Hampshire by large margins. If Clinton fails to win Iowa and New Hampshire she at least needs to come in a close second and then hope that she can win South Carolina to stem the tide.