Mr. Hayes, a liberal intellectual who has hosted a well-regarded weekend morning program on MSNBC for the past 18 months, is a protege of Rachel Maddow, the highest-rated host on the channel. He will become the lead-in for her 9 p.m. program, “The Rachel Maddow Show.”

The change is predicated on the belief that MSNBC can win a wider audience with Mr. Hayes than it did with Mr. Schultz, a champion of the working class whose bluster didn’t always pair well with Ms. Maddow and the channel’s other prime time program, “The Last Word with Lawrence O’Donnell.” Mr. Hayes, on the other hand, is just as wonky as Ms. Maddow and Mr. O’Donnell, and is a regular contributor to both of their programs…

“Up” doesn’t have a huge audience — it had about 139,000 viewers ages 25 to 54 last month — but it consistently beats CNN on Saturday and Sunday mornings, and it has been praised by media critics for allowing long, thoughtful conversations about politics and public policy, the kind rarely seen elsewhere on television. These conversations usually project a liberal worldview, in line with MSNBC as a whole.