What a difference four years can make.

Presidential candidates, from unknowns to frontrunners, are able to reach citizens like never before thanks to the quick-acting power of social media.

A simple tweet or Facebook post can reach millions, any time of the day or night. The candidates know it, and they're taking advantage.

Chris Christie's town hall from Iowa was streamed live Wednesday.

Donald Trump has been insulting outsiders - contenders or not - every chance he gets.

According to Ben Dworkin, director of the Rebovich Institute for New Jersey Politics at Rider University, today's presidential candidates are dominating the political news agenda - a job that belonged to a few dominant newspapers in the past.

"Whatever they had in their headlines, that's what everybody else seemed to talk about; that's no longer the case," Dworkin said. "What Donald Trump gets to tweet at 2:00 in the morning becomes what everybody's online version of their paper is talking about the next day."

Social media has transformed the electoral landscape, Dworkin said, but is that a good or bad thing?

On one hand, sites like Twitter and Facebook are opening the door of politics to countless people who otherwise may never have cared at all.

But people may be paying attention to the wrong material, or for the wrong reasons.

"You have a situation where the flamboyant, the outrageous, and not necessarily the substance, is what's being talked about," Dworkin said. "We're talking about whatever anybody wants to tweet in 140 characters in order to provoke a reaction from others."

In any case, a social media presence is a must in order to have a chance at victory next November. A modern, sophisticated campaign is neither modern nor sophisticated without a Twitter handle or Facebook profile.