Fox News’ 11 p.m. Et “Gutfeld!” finally beat every other late-night show — including Stephen Colbert’s “Late Show” on CBS — Tuesday in total viewership and the advertiser-coveted age demographic of 25 to 54. When the right-leaning program debuted in April, host Greg Gutfeld and his promotional team made no secret of their ambition to overtake late-night rivals, but Colbert blocked him from the top spot.

On Tuesday night, “Gutfeld!” took in a total average of 2.120 million viewers, with 434,000 in the key demo, on average. The “Late Show,” which has an 11:35 p.m. Et start time on CBS, grabbed an average of 1.896 million total viewers of whom 423,000 were in the demo. Jimmy Fallon’s “Tonight Show” — an NBC program which also airs at 11:35 — came next with 1.216 million total viewers, on average, and 354,000 in the demo.

In the 18-to-49 demo, however, Colbert still won, averaging 322,000 viewers to Gutfeld’s 281,000 and Fallon’s...