On social media, journalistic news products compete with entertainment-oriented and user-generated contents on two different stages of news use: First, users navigate their attention through a continuous stream of information in their newsfeed and, second, they potentially click on some of these posts to spend time with the actual full-contents. The present study conceptualizes these two types of news use behaviors in social media environments as first- and second-level selective exposure. Based on this new approach, we investigated main drivers of journalistic news exposure on both exposure levels in an online survey experiment before the German federal election in 2017 (N = 210). To achieve high ecological validity, we developed a Newsfeed Exposure Observer (NEO)-Framework to recreate realistic user settings for online experiments studying selective exposure in the digital era, where news posts are complemented by popularity cues like social endorsements or individual recommendations. Findings show that, at the first level of selective exposure, attention to journalistic news posts is particularly affected by political interest. However, the decision to click on posts in the newsfeed and to spend time with the linked contents seems more strongly driven by social factors than by individual predispositions.