ABC News, CBS News, CNN, C-SPAN and Fox News sent a joint letter to the chairman of the South Carolina Democratic Party to protest its decision to provide MSNBC with exclusive TV and streaming rights to the state party's convention.

"The political parties have always had a tradition of open media access," executives from the networks wrote in the letter, whose contents were first obtained by TVNewser and then confirmed by The Hill.

"Your decision to restrict live coverage of your state party convention to a single news organization is the antithesis of openness. It is also concerning in that it could set a precedent that would end up seriously limiting citizen access to other key presidential electoral events."

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"We ask that you reverse this decision and allow your state party convention to proceed without any restrictions in media coverage. Doing so will provide the public with the widest opportunity to see and hear all the Democratic candidates as well as South Carolina's state and local party officials," it concludes.

The letter comes after the South Carolina Democratic Party this week announced that it had granted MSNBC "exclusive rights" to the event, which will attract 21 of the 24 Democratic presidential candidates.

The state party also warned that "any footage taken by other outlets may not be aired live."

C-SPAN's Steve Scully told The Hill earlier this week that the network is "deeply disappointed" in the state party's decision.

MSNBC's exclusive coverage is being anchored by Joy Reid and Al Sharpton, a former Democratic presidential candidate.

-- Updated at 4:35 p.m.