At The Fix, Philip Bump’s “How the Internet has democratized democracy, to Bernie Sanders’s benefit” sheds light on the power of social media as a force for political education and change. Commenting on the insights of NYU professor Clay Shirky, author of “Here Comes Everybody: The Power of Organizing Without Organizations,” Bump explains:

…The gist is this. The two-party system necessarily can’t encompass every viewpoint. So, to hold parties together, some things became unmentionable. As media options broadened and the press wasn’t acting as gatekeeper, candidates could talk to voters more directly. But they still largely needed the resources of the party in order to get elected, so they still hewed to the rules about what couldn’t be mentioned.
Until 2008, when Barack Obama mastered talking to, fundraising from and turning out a large population.
“Reaching & persuading even a fraction of the electorate used to be so daunting that only two national orgs could do it,” Shirky wrote. “Now dozens can. This set up the current catastrophe for the parties. They no longer control any essential resource, and can no longer censor wedge issues.” The result, he says, is the “quasi-parlimentarianism” of the moment: The Democratic Party, the Republican Party, the Trump Party and the Sanders Party, all vying for power and the presidency…Trump and Sanders can ignore the established parties by talking directly to the voters.

Thanks to the internet and social media, now candidates can define their political personas without as much help from their respective political parties. The “Internet has “democratiized democracy,” as Bump puts it.
The other factor referenced by Bump is cell phones. Bump quotes from Jill LePore’s New Yorker article describing a recent rally for Hillary Clinton:

The instant Clinton began speaking, dozens of arms reached high into the air, all across the room, wielding smartphones. It was like watching a flock of ostriches awaken, the arms their necks, the phones their heads, the red recording buttons their wide, blinking eyes.

Bump adds, “That ceaseless documentation of the moment made individuals in the crowd often indistinguishable from reporters…The media has a role, as do the political parties. The role of each was once to serve as gatekeeper. Now, the role is often to serve as bullhorn.”
Trump’s TV presence surely fueled his success as a GOP presidential candidate. He began his white house run with name recognition few political leaders could hope to match. Plus, he understood how to leverage media to get free publicity worth millions of dollars.
A few weeks ago, I noted that, with respect to advertising,

Online ad share is growing fast. But broadcast television still rules, when it comes to ad budgets and is projected to account for about $8.5 billion of the $11.4 total ad spending for 2016, compared to about $1 billion for digital media, according to Issie Lapowsky, writing in Wired. But Larry Grisolano, who supervised political ads for the 2008 and 2012 Obama campaigns, predicts that in 2016 presidential campaigns will allocate “nearly a quarter of their spending to digital media.”

Yet, it’s not as much about the ads, as peer contact and sharing in social media, particularly facebook, which is so easy to use and where anyone can share print, video and photos. You can’t do that in newspapers and TV.
A well-circulated YouTube clip likely meets more persuadable eyeballs than the most carefully-crafted letter to the New York Times. Peer to peer contact is critical for enhancing voter turnout. But it’s also important for forming and changing political attitudes.
The success of the Sanders campaign owes much to social media. Sanders does not have a flashy TV persona, as does Trump, and to a lesser extent, Clinton. His sincerity comes across well on television. But his more effective tool is social media, which helps to explain his soaring popularity with younger voters.
A candidate can get a lot of bang for the buck recycling YouTube clips on facebook and other social media to reach younger voters. Democrats seem to have more leverage with these tools at the moment. I’m seeing a vigorous debate between Clinton and Sanders followers on facebook and twitter.
Hillary Clinton can be an extremely effective communicator, frequently comes across as the most knowledgeable candidate in televised debates, and generally does well in TV, radio and print interviews. But the Clinton campaign has some catch-up to do to reach the youth demographic on social media.
One of the best things about social media is that it can’t be smothered by the Koch brothers or any other wealthy conservative financiers. A staged political ad is always going to have less cred with swing voters than a heartfelt share on fb. This may come in handy in the final weeks of the general election.