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On Friday, Nov. 6, MSNBC host Rachel Maddow will be at Winthrop University in Rock Hill, S.C. So will former secretary of state Hillary Clinton. So will former Maryland governor Martin O’Malley. So will Sen. Bernie Sanders. All of them are seeking the Democratic presidential nomination, and all of them will be interviewed by Maddow on that day.

Just not together. Rules set out by the Democratic National Committee (DNC) allow Maddow to interview these three candidates sequentially — in a format known as a “forum” — but not jointly, as in a “debate.”

Which really stinks. “Everybody who works in this business would love to be in position of having all the candidates” on the stage at the same time, concedes Maddow, who is nonetheless excited to be participating in the co-called “First in the South Candidates Forum,” which is hosted by the South Carolina Democratic Party, among other entities including the Southern State Democratic Parties.

Blame “exclusivity” for the formatular madness. Back in May, the DNC announced that there’d be six sanctioned debates spread through the campaign season, starting with the CNN debate next week in Las Vegas and ending in February or March in Wisconsin. The party leveled a threat at candidates who would dare exercise their freedom of assembly and freedom of speech to debate outside of those parameters: “Any candidate or debate sponsor wishing to participate in DNC debates, must agree to participate exclusively in the DNC-sanctioned process,” noted the DNC. “Any violation would result in forfeiture of the ability to participate in the remainder of the debate process.”

We turned to Jaime Harrison, chair of the South Carolina Democratic Party, for some guidance on what things could legally happen in a “forum” versus what things could happen in a “debate.” Here’s what he said: “The candidates can’t engage in the back and forth because it denotes more of a debate than an actual forum. … They cannot engage in asking each other questions or being asked the same question while on stage.” Got that, Maddow, Clinton, O’Malley and Sanders? None of that prohibited stuff!

Maddow will engage each of the candidates in prolonged, sequential discussions. The approach, says Harrison, will enable Maddow and the candidates to “get into some substance” as opposed to the clipped and hurried discussion that often plagues debate formats.

Fair enough. But we wondered what would happen if, say, O’Malley burst onto the stage and took issue with an answer Clinton gave to Maddow, would he be banned from bona fide debates? Would Clinton be banned if she responded? “I appreciate the invitation to speculate but for us … [the] debate next Tuesday in Nevada, is about the candidates who will take the stage and their vision to move America forward,” wrote Luis Miranda, the DNC’s communications director.

These questions land on top of a debate that pits the principles of democracy against political optics. For strategic reasons, the DNC limited the sanctioned debates to six occasions. As The Post’s Greg Sargent has reported, the Clinton camp wanted four debates and O’Malley wanted many more. “When 24 million people are tuning in to watch the Republican sideshow, it begs the question why the Democratic National Committee is holding debates on holiday weekends and Friday nights,” said O’Malley spokesperson Haley Morris. “It’s almost as if they want to make sure as few people as possible get to see them.”

A pair of DNC vice-chairs — Hawaii Rep. Tulsi Gabbard and former Minneapolis mayor R.T. Rybak — last month issued a public call for more debates. Noting such dissension, Maddow sounds animated, “Intra-Democratic Party fighting is this, like, rare species in American politics,” she says. In 2008, there were more than 20 Democratic debates, though only six were sanctioned by the DNC; there was no exclusivity requirement.

Whatever the larger political picture, Maddow will have to make these one-after-the-other interviews come alive, not an easy task when the candidates have been giving interview after interview. Clinton, who cordoned herself off from the media earlier this year, has been on an interviewing tear of late, taking questions from Maddow’s colleagues on NBC/MSNBC — Andrea Mitchell and Chuck Todd — as well as several other outlets. E-mail questions have abounded. “There’s a meta element to the questioning on the e-mails that I find a little bit boring — like when Secretary Clinton is being asked about the e-mails and most of the questions are why she keeps getting asked about the e-mails,” says Maddow.

Perhaps Maddow should compare notes with MSNBC colleague Joe Scarborough, name partner on the network’s morning program. “The follow-up questions just never come,” says Scarborough about the numerous TV interviews of the front-running Democratic candidate. Question No. 1, says the host, is who at the State Department authorized Clinton’s homebrew e-mail server? The next one is why won’t she turn over the server? Clinton, says Scarborough, issues the “same pat answers that every journalist who interviews her knows is coming.”

Whatever Maddow asks Clinton, it’ll be their first time together in an interview. Her job, she says, is to draw out the emerging policy differences among the candidates, an undertaking that may well involve some watchable testiness onstage. Back in August, America enjoyed the spectacle of Fox News hosts showing no mercy toward Republican hopefuls. Maddow can harness that very same energy as well. “People deride so-called partisan media,” says Maddow. “I don’t see us as being partisan I see us as being honest about where we are,” she says about her work at MSNBC. “Listen, I’m a liberal. Here’s how I see this story.”