Writing for Daily Kos, Silver gained a following, especially for his primary election forecast on Super Tuesday, February 5, 2008. From that primary election day, which included contests in 24 states plus American Samoa, Poblano predicted that Barack Obama would come away with 859 delegates, and Hillary Clinton 829; in the final contests, Obama won 847 delegates and Clinton 834.

FiveThirtyEight, an American website focusing on opinion poll analysis, politics, economics, and sports blogging, was founded by analyst Nate Silver. The website's name is derived from the number of electors in the United States electoral college.

FiveThirtyEight gained national attention for outperforming most pollsters' projections in the North Carolina and Indiana Democratic party primaries. Silver relied on demographic data and the history of voting in other states during the 2008 Democratic primary elections.

Silver revealed his true identity to his FiveThirtyEight readers.

FiveThirtyEight began providing regular updates on projections for the 2008 U.S. Senate races. The projections, which relied on both polls and demographic analysis, were updated weekly.

FiveThirtyEight became the first blog ever selected as a Notable Narrative by the Nieman Foundation for Journalism at Harvard University.

In the final update of his presidential forecast model, Silver projected a popular vote victory by 6.1 percentage points for Barack Obama and electoral vote totals of 349 (based on a probabilistic projection) or 353 (based on fixed projections of each state). Obama won with 365 electoral college votes.

FiveThirtyEight earned a Bloggie as the Best Weblog about Politics in the 9th Annual Weblog Awards.

FiveThirtyEight devoted more than a dozen articles to the Iranian presidential election in June 2009, assessing of the quality of the vote counting.

FiveThirtyEight covered the November 3, 2009, elections in the United States in detail.

FiveThirtyEight turned its focus to the United Kingdom general election scheduled for May 6, with a series of more than forty articles on the subject that culminated in projections of the number of seats that the three major parties were expected to win.

FiveThirtyEight writers gave extensive coverage to the Massachusetts special election to the U.S. Senate. The "538 model" once again aggregated the disparate polls to correctly predict that the Republican Scott Brown would win.

Silver announced that in early August the blog would be relaunched under a NYTimes.com domain.

The New York Times and Silver announced that FiveThirtyEight had formed a partnership under which the blog would be hosted by the Times for a period of three years.

FiveThirtyEight posted pollster rankings that updated and elaborated Silver's efforts from the 2008 election. Silver expanded the database to more than 4,700 election polls and developed a model for rating the polls that was more sophisticated than his original rankings.

The transition took place with the publication of Silver's first FiveThirtyEight blog article online in The New York Times. The first column of the renamed FiveThirtyEight: Nate Silver's Political Calculus appeared in the Times with the introduction of U.S. Senate election forecasts.

FiveThirtyEight won a Webby Award for Best Political Blog from the International Academy of Digital Arts and Sciences in the 16th annual Webby Awards.

FiveThirtyEight rolled out its 2012 general election forecasting model. In the initial forecast, Barack Obama was estimated to have a 61.8% chance of winning the electoral vote.

Silver's model gave President Obama a 90.9% chance of winning a majority of the electoral votes. The 538 model correctly predicted the winner of all 50 states and the District of Columbia.

Silver and his FiveThirtyEight blog departed The New York Times and joined ESPN. Silver served as the editor-in-chief of the site and built a team of journalists, editors, analysts and contributors.

FiveThirtyEight launched its ESPN webpage. The lead story by Silver explained that FiveThirtyEight is a data journalism organization.

FiveThirtyEight introduced its forecasts for each of the 36 U.S. Senate elections being contested that year. At that time, the Republican Party was given a 64 percent chance of holding a majority of the seats in the Senate after the election.

FiveThirtyEight was named the Data Journalism Website of the Year for 2016 by the Global Editors Network.

The final prediction by FiveThirtyEight on the morning of election day had Hillary Clinton with a 71% chance to win the 2016 United States presidential election.

It was announced that FiveThirtyEight would be transferred to ABC News from ESPN, Inc., majority owned by The Walt Disney Company.

FiveThirtyEight announced that for their 2020 general election forecast they had designed a new graphical structure. This included going with modular structure, a "ball swarm" design for the chart depicting each candidate's chances, and the addition of a "forecast mascot" named Fivey Fox.

Silver announced that he would be leaving the site amid widespread layoffs at ABC News, who said the website would be "streamlined" ahead of the 2024 election cycle; editor Chadwick Matlin was among the many laid off. According to Silver, two thirds of FiveThirtyEight's staff were cut in one day.

The original website domain at fivethirtyeight.com was closed, with web traffic becoming redirected to ABC News pages, and its logo was replaced, with the name 538 used instead of FiveThirtyEight.

The Walt Disney Company shut down 538 and laid off about 15 employees. ABC News announced that it would continue to provide polling data and analysis outside of the 538 brand.