Incumbent President Jimmy Carter was again selected as the nominee through a series of primary elections and caucuses, culminating in the 1980 Democratic National Convention, held from August 11 to 14, 1980, in New York City.

Carter faced a major primary challenger in Senator Ted Kennedy of Massachusetts, who won 12 contests and received more than seven million votes nationwide, enough for him to refuse to concede the nomination until the second day of the convention.

Carter would be the last incumbent president to lose a primary in any contest until Joe Biden lost to Jason Palmer in the 2024 American Samoa Democratic presidential caucuses.

[4] In January 1979, shortly after Iran's leader Shah Mohammad Reza Pahlavi fled the country, lead Iranian opposition figure Ayatollah Ruhollah Khomeini returned from a 14-year exile and with the help of the Iranian people toppled the Shah which in turn led to the installation of a new government that was hostile towards the United States.

Gallup had him beating the president by over two to one, but Carter remained confident, famously claiming at a June White House gathering of Congressmen that if Kennedy ran against him in the primary, he would "whip his ass.

Kennedy gave an "incoherent and repetitive"[9] answer to the question of why he was running, and the polls, which showed him leading the President by 58–25 in August now had him ahead 49–39.

[10] Meanwhile, U.S. animosity towards the Khomeini régime greatly accelerated after 52 American hostages were taken by a group of Islamist students and militants at the U.S. embassy in Tehran and Carter's approval ratings jumped in the 60-percent range in some polls, due to a "rally ‘round the flag" effect[11] and an appreciation of Carter's calm handling of the crisis.

Carter decisively defeated Kennedy everywhere except Massachusetts, until impatience began to build with the President's strategy on Iran.