Looking at the sum total of mentions of both terms, we see that mentions soared from around September 2011, peaked in the first few months of 2012, then ramped down through 2014 and have been fairly stable in the years since. Interestingly, Fox News and MSNBC/MSNOW used to mention the terms substantially more than CNN, with MSNBC ramping down its mentions through 2016 to match CNN and Fox News remaining elevated through mid-2023, with all three channels now mentioning the terms fairly similarly, with Fox News a bit elevated. Combined, the three channels have mentioned "conservatives" 2.27 times more than "liberals" over the past decade and a half.
From the timeline below, we can see the huge late-2011/early-2012 surge was driven by mentions of "conservatives":
In contrast, mentions of "liberals" increased during this period, but not as sharply or tightly. Fox News clearly dominates mentions through present, though until late 2015, MSNBC fell between Fox News and CNN in its monthly mentions.
