In today's media invironment, can there really be that much difference after the conventions.

In today's media environment with the internet,social media and 24 hour news channels, is it really possible to have a big swing in support between one candidate for president and another after the conventions or later in the race. The last time that I recollect that happening was the Dukakis/Bush race, which was before the internet really took hold. Since then we have had Clinton/Bush, Clinton/Dole, Bush/Gore, Bush,Kerry,Obama/McCain ,Obama/Romney. The only time in any of those elections, we have had somewhat of a swing was with the economic crash of 2008, which was an incident beyond the control of the candidates.
We have heard the proclamations from the Clinton people about what the Republicans are going to do to Sanders, if he gets the nomination. I would bet, that if you got 100 random registered voters in a room and asked them: "Bernie Sanders,socialist, how many people have heard of that", virtually all of them would raise there hand.