Rachel Maddow went on vacation and missed her Mondays-only program this week, resulting in MSNBC having its smallest Monday audience in the advertiser coveted demographic during her time slot since 2015. 

Maddow, who makes roughly $30 million per year, only works once a week after scaling back her workload earlier this year to pursue other projects. But Alex Wagner, who was selected to replace her on Tuesday through Friday, has struggled to resonate with viewers since she took the job about a month ago. Things took a turn for the worse Monday when she was given a chance to host the 9 p.m. ET hour for an entire week.

MSNBC's Rachel Maddow

Rachel Maddow, who makes roughly $30 million per year, announced earlier this year that she would only host "The Rachel Maddow Show" once a week, on Monday evenings, so that she could focus on other projects.  (FOX)

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Wagner filled in for Maddow, who is on vacation, and the result was an average audience of only 119,000 viewers among the key demo of adults ages 25-54 for MSNBC’s least-watched 9 p.m. hour in the category on a Monday since 2015.

The last time MSNBC performed that poorly in the critical category was on June 15, 2015, when Maddow averaged only 116,000 viewers. 

Maddow’s decision to avoid television cameras whenever possible have plagued MSNBC and her latest vacation came the week after Wagner dipped to 129,000 average demo viewers and delivered its worst night ever on Friday when less than 100,000 viewers from the category tuned in. 

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Rachel Maddow

MSNBC’s Rachel Maddow only hosts the network’s 9 p.m.  ET program on Monday evenings after scaling back her workload.  (Getty Images)

Earlier this year, Maddow took several weeks off only to announce she would only she would only work a fifth of the time shortly after her return. Wagner, who NewsBusters associate editor Nicholas Fondacaro recently dubbed a "glorified understudy," was given the chance to fill Maddow’s void despite being previously canceled by MSNBC. 

In 2015, MSNBC canceled her dayside program "Now" after a four-year run. At the time, MSNBC claimed Wagner's show was among those cut as part of a programming reshuffling in order to shift daytime towards straight news – but the program’s ratings were not exactly desirable.

Alex Wagner Rachel Maddow

MSNBC named Alex Wagner as Rachel Maddow’s replacement four nights per week and  whenever the "Rachel Maddow Show" namesake needs a vacation.  (MSNBC)

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The 152 episodes of "Now" that aired in 2015 before it was canceled averaged only 328,000 total viewers and 49,000 among the demo to trail Fox News by over 280% in each measurable. Then in 2016, MSNBC scrapped a weekend show Wagner was set to launch after the network previously announced the program. 

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All data courtesy of Nielsen Media Research. 

Fox News' Joseph A. Wulfsohn contributed to this report.