Rachel Maddow has been in a league of her own as MSNBC's biggest star, whose viewership far exceeds any of her colleagues. 

Monday marks the beginning of her hiatus from primetime as she pursues various projects including podcasts and even a film collaboration with Ben Stiller and Lorne Michaels, telling viewers last week she will return in April but will make occasional appearances on MSNBC, including for the network's coverage of President Biden's State of the Union address in March. 

The network indicated that it would have rotating hosts filling in during that period with MSNBC host Ali Velshi being the first.

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However, Maddow warned her fans that more hiatuses could come.

"There may eventually be another hiatus again sometime in my future, but for now we are just taking it one step at a time," Maddow told her views last week before assuring them they'd be in "very good hands" of the producers of "The Rachel Maddow Show." 

MSNBC host Rachel Maddow. (Photo by Virginia Sherwood/NBCU Photo Bank/NBCUniversal via Getty Images)

Maddow's hiatus follows numerous reports alleging she wanted to scale back her workload in primetime as she carries the weight of the entire network on her shoulders. 

"The Rachel Maddow Show" was MSNBC's most-watched show in 2021, averaging roughly 2.6 million viewers at 9 p.m. ET, trailing behind Fox News' "Hannity" at 2.9 million in the same time slot but far ahead of her primetime colleagues Lawrence O'Donnell and Chris Hayes, who averaged only 1.8 million and 1.6 million viewers respectively. 

Maddow is the only MSNBC host to consistently average above the 2 million-viewer benchmark and rank among the top ten most-watched cable news programs, the other nine being Fox News programs. 

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"She is by far their highest-rated host. She's the only one who remotely gets something that is competitive… but what we're gonna see is that MSNBC, like CNN, has little to no bench to backfill these spots," Fox News contributor Joe Concha told Fox News Digital. "I think you're going to see MSNBC struggle as mightily as it ever has in 2022 not seen since the days before Phil Griffin came along back before even Barack Obama was president."

Concha called out the liberal host for not being entirely "definitive" about her future on MSNBC's airwaves.

"If she doesn't want to do her show on a nightly basis, then just don't do it. Period," Concha said. "If she still wants to do that, then do it. But do this in kind of an in-between, on-the-fence kind of way will not be good for their numbers because the audience won't have anybody there that they can reliably count on to be there on a nightly basis."

MSNBC host Rachel Maddow. (Photo by: Nathan Congleton/NBCU Photo Bank/NBCUniversal via Getty Images via Getty Images)

NewsBusters managing editor Curtis Houck predicts her absence in the coming weeks will leave an "ice-berg-sized ratings hole" in MSNBC's schedule, particularly with a weak bench of talent that won't reach Maddow's level of viewership. 

"The only solace for MSNBC is at least they don't have a scandal involving two lead executives sleeping with each other with the staff having turned into basket cases," Houck told Fox News, referring to the ongoing turmoil plaguing CNN. 

MSNBC isn't the only network to struggle from the absence of its biggest star. CNN has been going through similar headaches ever since the firing of Chris Cuomo, who also hosted in the 9 p.m. ET time slot. 

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Cuomo was suspended by the poorly-watched liberal network following revelations from the New York Attorney General's investigation that aided his brother, ousted Democratic New York Gov. Andrew Cuomo, during his sexual harassment scandal than he previously acknowledged. But the CNN anchor was ultimately terminated after a sexual misconduct allegation from a former ABC News colleague emerged. 

CNN has used Michael Smerconish in Cuomo’s old spot, extended Anderson Cooper’s program and spent two weeks airing poorly rated "Democracy in Peril," specials hosted by Brianna Keilar and Jim Acosta, but none of the options have resonated with Americans. 

Rachel Maddow and Chris Cuomo have left gaping holes at MSNBC and CNN. 

Grabien Media founder and news editor Tom Elliott took a swipe at MSNBC's "mid-day mediocrities" he predicts will fill the void for Maddow during hiatus, saying the Peacock network "will soon suffer consequences of the progressive policies their pundits promote."

"When a news enterprise defines itself around opposition to a singular political figure, and then that figure leaves office, the news network becomes lost at sea," Elliott told Fox News Digital. "Lacking any kind of clear vision, or principled purpose, MSNBC and CNN are presently preoccupying themselves re-adjusting deck chairs as their networks sink ever deeper into the abyss."

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Cornell Law School professor and media critic William A. Jacobson feels holes at 9 p.m. are simply the latest signs that liberal networks are having trouble remaining relevant under President Biden. 

"CNN and MSNBC built their current brands around hatred of Donald Trump and conspiracy theories of Russia collusion that never held up. Now that Trump no longer is president and Biden is struggling, those networks don't seem to know what they want to be," Jacobson told Fox News Digital. "The loss of two marquee hosts for reasons unrelated to branding makes the identity problem worse."

Maddow declined to comment. 

Fox News' Brian Flood contributed to this report.