The general expectation was that, with President Barack Obama having the advantage of incumbency and being the only viable candidate running, the race would be merely pro forma.
Several of the lesser-known candidates made efforts to raise visibility. Some Occupy movement activists made an attempt to take over the Iowa caucuses, and managed to get about 2% of the vote for Uncommitted. With eight minor candidates on the ballot in New Hampshire, there was a debate at Saint Anselm College in Goffstown, New Hampshire on December 19, 2011, in which seven candidates participated. Pro-life activist Randall Terry bought time on television in order to show graphic commercials denouncing abortion.
Three candidates – other than Obama – who had been on the ballot in New Hampshire were also on the ballot in Missouri. One such candidate, Randall Terry, attempted to air graphic TV commercials during Super Bowl XLIV, but was met with resistance from various TV stations in some locations. The Democratic National Committee also tried to stop the ads by claiming that Terry was not a legitimate Democratic candidate even though he was legally on the ballot.
On May 8, 2012, Keith Russell Judd, an inmate serving a 210 month sentence, won 41% of the primary vote in West Virginia against incumbent Barack Obama, a higher percentage of the vote in one state than any other primary opponent of Obama had hitherto achieved in 2012. Shortly thereafter, attorney John Wolfe, Jr. won 42% of the primary vote in Arkansas after widespread speculation that Wolfe could possibly pull off an upset of the state. 
Challengers to President Obama had only qualified for the ballot in eight states – New Hampshire, Missouri, Oklahoma, Louisiana, Texas, West Virginia, Arkansas, and Alaska – while a ninth (Ohio) was going to have Randall Terry on the ballot, but removed his name before the ballots were printed.
Darcy Richardson suspended his bid for the nomination on April 28, 2012. He still appeared on the ballot in Texas after suspending his campaign.
The number of pledged delegates allocated to each of the 50 U.S. states and Washington, D.C. is based on two main factors: (1) the proportion of votes each state gave to the Democratic candidate in the last three presidential elections, and (2) the number of electoral votes each state has in the United States Electoral College. In addition, fixed numbers of delegates are allocated to Puerto Rico, American Samoa, Guam, the U.S. Virgin Islands, and Democrats Abroad under the party's delegate selection rules. Depending on each state's law and each state's party rules, when voters cast ballots for a candidate in a presidential caucus or primary, they may be voting to actually award delegates bound to vote for a particular candidate at the state or national convention (binding primary or caucus), or they may simply be expressing an opinion that the state party is not bound to follow in selecting delegates to the national convention (non-binding primary or caucus).
States are awarded bonus pledged delegates if they schedule their primary or caucus later in the primary season. Those states with April dates are awarded a 10 percent increase, while those who schedule from May 1 to June 12 get a 20 percent increase. And starting on March 20, a 15 percent bonus is awarded when clusters of three or more neighboring states begin on the same day.
The unpledged superdelegates will include members of the United States House of Representatives and Senate, state and territorial governors, members of the Democratic National Committee, and other party leaders. Because of possible deaths, resignations, or the results of intervening or special elections, the final number of these superdelegates may not be known until the week of the convention.
Some delegates committed to candidates other than the President, have not been permitted to be elected in contested primaries, for administrative reasons.
Florida's legislature set the date for its primary on January 31, violating the scheduling guidelines of the Democratic National Committee (DNC). The DNC has since declared Florida's primary as nonbinding, and therefore an alternate delegate selection system consisting of county caucuses will now take place on May 5, followed by a state convention in June.
Randall Terry collected 18% of the votes, winning twelve counties, in the Oklahoma primary, qualifying him for seven delegates to the 2012 Democratic National Convention. Jim Rogers collected 13% of the votes, winning three counties, qualifying him for three delegates (one from each of three congressional districts where he collected over 15%).
A Democratic presidential candidates debate, held at Saint Anselm College in December 2011, was attended by seven candidates; Obama did not participate. A total of 60,659 votes were cast in the primary. Obama won with 49,080 votes. The total votes cast were more than 30 percent fewer than in 1996, the last time that a Democratic president ran for re-election without significant opposition.