As Variety notes, the network has experienced an uptick in prime-time viewership in the days since special counsel Robert Mueller delivered his report on the Russia investigation. The network’s improved numbers come after several competitive months in the cable-news arena, where Fox News and MSNBC have been battling for supremacy.

As of today, Fox is in the lead, with both Sean Hannity’s 9 p.m. program, Hannity, and Tucker Carlson’s 8 p.m. show, Tucker Carlson Tonight, gaining over its rivals. On Wednesday, Variety notes, Hannity earned 4.3 million viewers; that’s more than a million more than it averaged in January. That same night, Tucker Carlson Tonight—which faced a boycott call earlier this month, when controversial comments from the host were re-surfaced—pulled in about 3.49 million viewers. Tucker averaged less than 3 million viewers a night in January.

Yet the surge could be short-lived, as cable-news ratings are famously fast-changing. Hannity and MSNBC’s The Rachel Maddow Show have effectively been trading off the top spot, ratings-wise, all year: Maddow won January, while Hannity took February. With both hosts now going deep on the Mueller report and its fallout, expect their shows to continue the back-and-forth ratings battle throughout the spring.