The cable network will carry speeches and interviews with the 21 candidates confirmed to participate. (Reuters)

The South Carolina Democratic Party is hosting perhaps the largest gathering of Democratic presidential candidates in history this weekend, but Fox News won’t be allowed to cover it live. Neither will C-SPAN, CNN nor any other TV network not named MSNBC.

In an unusual arrangement, the state party has granted exclusive live TV and streaming rights to its convention to MSNBC.

The cable network will carry speeches and interviews with the 21 candidates confirmed to participate, including former vice president Joe Biden. But by party decree, every other network must wait until three hours after the candidates speak to air anything — a lifetime in the news business. The party has also banned live-streaming.

This naturally hasn’t gone over well with the other news networks, which have protested their exclusion from an event that traditionally had been open to all on an equal basis.

“It’s very odd,” Steve Scully, C-SPAN’s political editor, said in an interview. “I confronted the party and asked them why. They said a decision had already been made.”

C-SPAN had planned to provide gavel-to-gavel coverage of Saturday’s event, in which the candidates will speak for seven minutes each, as part of its ongoing “Road to the White House” series. It had promoted its coverage of the South Carolina event on the air, too.

Now, no deal.

C-SPAN will skip the event in protest and will move its cameras and crew across the state capital, Columbia, to cover a candidate forum hosted by Planned Parenthood, Scully said.

“It’s puzzling. It’s ridiculous,” he said. “They’re missing out” on exposing the candidates to more viewers.

A Fox News spokeswoman, Katie Cwayna, said the network had lodged a complaint with the party after being “banned” from the event.

However, a party spokesman, Tim Sullivan, disputed that characterization. He said no news organization has been banned outright from coverage, although TV stations will have to abide by the delay, giving MSNBC a clear field.

MSNBC negotiated a three-hour exclusive window covering the candidates’ presentations, said spokesman Errol Cockfield, but isn’t obligated to carry the entire event, which is expected to last about nine hours.

Sullivan said MSNBC was given exclusive rights after it agreed to carry the speeches and provide one-on-one interviews with the candidates (its coverage will be hosted by Joy Reid and Al Sharpton).

“We thought providing that level of access was unique to a state party,” said Sullivan, who said no money changed hands. “We think it’s a very exciting way” to present the meeting to viewers.

Both the Democratic and Republican national committees grant exclusive live TV rights to their primary debates (the DNC decided in March to exclude Fox News from consideration, citing its alleged bias). But lesser events, such as party conventions, are typically open to all comers without restrictions.

The South Carolina Democratic Party’s exclusive arrangement with MSNBC was first reported by the Washington Examiner on Tuesday.

A CNN spokeswoman didn’t respond to a request for comment.