For now, at least, Hillary Clinton has a 76 percent chance of defeating Donald Trump to become president of the United States. A victory by Mr. Trump remains quite possible: Mrs. Clinton’s chance of losing is about the same probability that an NBA player will miss a free throw.
This electoral probability, the first forecast by the Upshot’s presidential prediction model, is based on the voting history of each state and on roughly 300 state and national polls of the race conducted since mid-April.
The model suggests Mrs. Clinton is a strong favorite in 15 states, enough to give her 186 of the 270 electoral votes she needs to win the White House. Add to this eight states that polls currently show are leaning Democratic — including Minnesota, Michigan and Pennsylvania — and Mrs. Clinton would have 275 electoral votes and the presidency.
But, with 16 weeks remaining in the campaign, a lot can change. Using the same model, we would have said that Bill Clinton had less than a 20 percent chance to win the presidency with roughly four months to go in 1992. It was only after Ross Perot left the race and the Democrats rallied around Mr. Clinton after the Democratic convention that his polls improved. And they improved sharply. One month later, he was an 84 percent favorite.
This kind of polling volatility should be expected, particularly with party conventions at hand. It is one reason that Mrs. Clinton’s probability of victory is not higher. Current polling averages suggest a four-point victory in the national popular vote for Mrs. Clinton, if nothing changes. But we expect changes between now and Election Day.