Nearly three-quarters (74%) of Millennial Democrats who say they are very likely to participate in their state’s primary or caucus learned about the 2016 presidential election through a social networking site. This is starkly higher than the 50% of Millennial Republicans…

Source: Among Millennials engaged in primaries, Dems more likely to learn about the election from social media
My observation – before I read this study – is that Democrats and left-leaning groups largely own social media propaganda efforts, with relatively little high quality propaganda coming from Republicans or right-leaning groups. This might be a factor in the results of the survey, shown above.
Regardless of political affiliation, social media is the dominant source of information about the 2016 presidential election. Social media is also largely dominated by very loud, often wrong, propaganda messaging efforts.