The more than a dozen GOP White House hopefuls already have two debates under their belts, but Tuesday's encounter will mark the first such event for Democratic contenders.

CNN and Facebook are set to jointly host the first debate between frontrunner Hillary Clinton and her four party rivals -- former Rhode Island Gov. Lincoln Chafee, former Maryland Gov. Martin O'Malley, Vermont Sen. Bernie Sanders and former Virginia Sen. Jim Webb, the Washington Post reported.

Joe Biden, meanwhile, has also been invited to join, but it is unlikely that the undecided vice president will jump into the presidential race ahead of the Las Vegas encounter moderated by Anderson Cooper, Dana Bash and Juan Carlos Lopez, according to Politico.

Despite Clinton's commanding lead in the polls, Tuesday's debate will mark only the opener of a number of such events already scheduled before and during the primary season, according to the Washington Post. Here are the other events already confirmed by the Democratic National Committee (DNC):

  • The Democratic candidates will meet on Dec. 19 in the critical early-primary state of New Hampshire, which is set to hold its nominating contest some time in February. This debate will be hosted by ABC and WMUR, the network's affiliate in Manchester, New Hampshire.

  • Whoever remains in the race is also scheduled to debate on Charleston, South Carolina, on Jan. 17, 2016, for an encounter hosted by NBC and the Congressional Black Caucus Institute. The Palmetto State's primary is expected to immediately follow the one in New Hampshire this election season.

  • Two more debates, finally, are expected around February and March of next year: The first, hosted by the Spanish-language television channel Univision and the Washington Post, will take place in Miami; the other, hosted by PBS, in Wisconsin.

A DNC vice chairwoman, who urged her party to add even more events, claimed that she was disinvited from Tuesday's debate because of her suggestion, the Hill reported.

"When I signed up to be vice chair of the DNC, no one told me I would be relinquishing my freedom of speech and checking it at the door," Hawaii Rep. Tulsi Gabbard complained.

The committee, for its part, denied Gabbard's allegation through an unidentified spokesperson, the Hill added.