CBS' 'Late Show' ekes out a demographic win over NBC's 'Tonight Show' for the first time in more than 20 years while increasing its total-viewer lead.

By the slimmest of margins, there's a new No. 1 in late night.

CBS' The Late Show With Stephen Colbert will claim the No. 1 ranking in late night among adults 18-49 for the 2018-19 season, which ends Wednesday. It will mark the show's first season-long demographic win over NBC's The Tonight Show Starring Jimmy Fallon since Colbert took over as host in 2015 — and the first for The Late Show since 1994-95, in the early years of David Letterman's tenure.

The Late Show is also set to finish first in total viewers for the third consecutive season.

Colbert took over the 18-49 lead in early March by a mere hundredth of a point, averaging 16,000 viewers in the demographic at that point. That slim lead stayed stable through the end of the season: As of May 17, The Late Show is averaging 677,000 viewers in the demo (a 0.52 rating) to 659,000 (0.51) for The Tonight Show. ABC's Jimmy Kimmel Live! is in third place at 0.38, equal to about 486,000 viewers in the demo.

At the end of the 2017-18 season, The Tonight Show had a lead of about 72,000 viewers in the 18-49 demo, so the turnaround for The Late Show year to year is 90,000 viewers.

All three 11:35 p.m. shows are down year to year in the demo, consistent with earlier points in the season. The Tonight Show has fallen 25 percent from the same point in 2018; Jimmy Kimmel Live! is off by 19 percent and The Late Show by 12 percent.

In total viewers, The Late Show's 3.81 million viewers leads The Tonight Show's 2.44 million and Jimmy Kimmel Live!'s 2.04 million. Colbert has extended his lead a bit year to year, from 1.2 million to 1.37 million.

At 12:35 a.m., NBC's Late Night With Seth Meyers (0.3 in adults 18-49, 1.45 million viewers) remains in front of CBS' The Late Late Show With James Corden (0.23, 1.35 million). The final season of Last Call With Carson Daly on NBC averages a 0.18 in adults 18-49 and 733,000 viewers at 1:35 a.m.