At 50 minutes to airtime, the Rev. Al Sharpton, in pinstripes and cufflinks, was sitting in his office at Rockefeller Center, tinkering with Tuesday’s introduction to “PoliticsNation,” his new nightly show on MSNBC.

Two TV sets hung from the wall: one tuned to “Hardball,” the other to CNN. A procession of producers — he has six on staff — whisked through to give him updates on their segments. Just before he rose for his makeup session, he turned to his executive producer. “Let’s not forget,” Mr. Sharpton said, casually employing the TV vernacular, “to put that Ron Paul sound bite in the D-block.”