In doing so, she had become the first woman to ever be the presumptive nominee of any major political party in the United States.
On July 22, the Democratic National Committee email leak was published by Wiki Leaks as part of an alleged operation by the Russian government to boost Republican nominee Donald Trump and undermine Hillary Clinton.
The electoral battle turned out to be more competitive than expected, with Sanders winning the New Hampshire primary while Clinton scored victories in the Nevada caucuses and South Carolina primary.
On four different Super Tuesdays, Clinton secured numerous important wins in each of the nine most populous states including California, New York, Florida, and Texas, while Sanders scored various victories in between.
For her part, Clinton, who had won the state eight years prior in the 2008 Nevada Democratic caucuses, hoped that a victory would allay concerns about a possible repetition of 2008, when she ultimately lost to Obama despite entering the primary season as the favorite for the nomination.
Sanders, who attained 47.3% of the vote, was projected to receive five fewer pledged delegates than Clinton and the result was not promising for the following weekend's primary in South Carolina, more demographically favorable to Clinton than the prior contests.
The speculation centered on the prospects of Clinton, then-Secretary of State, making a second presidential bid in the 2016 election. He described his candidacy as a referendum on electoral reform legislation, prioritizing a single issue: the Citizen Equality Act of 2017, a proposal that couples campaign finance reform with other laws aimed at curbing gerrymandering and ensuring voting access.
Despite being heavily favored in polls issued weeks earlier, Clinton was only able to defeat Sanders in the first-in-the-nation Iowa Caucus by the closest margin in the history of the contest: 49.8% to 49.6% (Clinton collected 700.47 state delegate equivalents to Sanders' 696.92, a difference of one quarter of a percentage point).
A draft movement was started to encourage Massachusetts Senator Elizabeth Warren to seek the presidency, but Warren declined to run.
Although the results overall were unfavorable for Sanders, his four wins and narrow loss allowed him to remain in the race in anticipation of more favorable territory in New England, the Great Plains, Mountain States and the Pacific Northwest.
Sanders found more hospitable ground on the weekend of March 5, 2016, winning caucuses in Kansas, Maine and Nebraska by significant margins.
Prior to the Iowa caucuses on February 1, 2016, Webb and Chafee both withdrew after consistently polling below 2%.
his campaign after a distant third-place finish, leaving Clinton and Sanders the only two candidates.
He then laid off a majority of staff after the New York primary and Clinton's multi-state sweep on April 26.