They are describing selective coverage, something that the authors also accuse CNN of.Polite words from the report. The partisan media is Fox news.Second, our results indicate challenges that partisan media may pose for democratic account-
ability. Our findings suggest that partisan media may affect voters’ choices at least in part because
it hides information about aligned incumbents’ failures and distorts perceptions of political rivals.
This suggests that partisan media does not only present a challenge for the opposing party, it may
present a challenge for democracy which may deserve attention from policymakers.
By this definition of 'lying', your thread title could have been 'FOX viewers less likely to believe FOX lies after being exposed to CNN lies'.