This group of superdelegates includes every sitting Representative, Senator, and governor, as long as that person is a member of the Democratic Party. Also in the group of superdelegates are members of the Democratic National Committee, such as mayors and county executives (again, as long as they are members of the Democratic Party), and certain other select Democratic Party officials. Unlike other delegates who are pledged to vote for a certain candidate based on primary or caucus results, superdelegates can cast their votes at the national nominating convention for whichever candidate they want. Superdelegates have the option of revealing their preference before the convention.

The Republican Party does not employ superdelegates.

Beginning with the 2020 Democratic Party Nominating Convention (for which a location has yet to be announced), superdelegates will not vote on the first ballot unless the nominee is already assumed, based on the results of the party's primaries and caucuses. Rather, the superdelegates will hold their votes until at least the second ballot and then could help break a deadlock. In many cases, this will result in the superdelegates' having much less influence in selecting the eventual nominee because even if one candidate has not theoretically won enough primaries and caucuses to secure enough pledged votes to succeed on the first vote, that first vote has, in practice, resulted in the selection of a nominee.

Because the superdelegates have in the past made their preferred candidate known ahead of time and have then been allowed to vote on the first ballot, they have been counted in pledged delegate tallies alongside those acquired as the result of primary and caucuses victories. In the most recent example, Hillary Clinton was the preferred choice of a large majority of superdelegates and so her expected vote total leading up to the 2016 Democratic National Convention in Philadelphia included several hundred votes that, under the new scenario, would not have been known until the time of the convention.

The action taken by the Democratic National Committee (DNC) came as the result of a unanimous vote, in an effort by the party to show unity for reform. The DNC also encouraged states that have presidential caucuses, which require in-person attendance for a sustained period of time, to primaries, which require only a brief period of time; at the least, the DNC said, states having caucuses should offer some form of absentee voting.

Superdelegates were created in 1982 as a way to avoid the kind of division created by a contentious 1980 election campaign, in which Massachusetts Senator Ted Kennedy ran a spirited challenge to the incumbent President, Jimmy Carter. The convention resulted in a renomination for Carter, but many Democrats did not vote for Carter in the end, and the Republican nominee, Ronald Reagan, won what turned out to be a close election.

To date, the tally of superdelegate votes has not overturned the talley of pledged votes.