Hillary Clinton refused to concede the presidential contest early Wednesday even as Donald J. Trump built a lead in a series of battleground states, upending months of polling that had given the advantage to Mrs. Clinton and putting him on the verge of seizing back the White House for Republicans.

Shortly after 2 a.m., John D. Podesta, the chairman of Mrs. Clinton’s campaign, addressed Democrats, saying that “they are still counting votes, and every vote counts” and declaring that “she is not done yet.”

Just after 11:30 p.m. Tuesday, Mr. Trump was declared the victor in Florida, earning him the state’s 29 electoral votes and giving him a more certain grip on the presidential contest with Mrs. Clinton. About two hours later, he added Pennsylvania to his column.
Reaction to the prospect of a Trump presidency rippled across the globe, with financial markets abroad falling as American television networks raised the prospect that Mrs. Clinton might lose. Asian markets were trading sharply lower, down around two percentage points, and in the United States, Dow Jones futures were down as much as 800 points in after-hours trading