Scott Blackburn and Luke Wachob oped in the OC Register:

So what changed? Why are presidential campaigns today a 24/7/365 affair?

There are innumerable reasons: the rise of television as a campaign medium, the increased role of early-state primaries and the decreased role of “back-room” party deals, to name a few.

But one overlooked cause may be campaign finance regulations, which, to fair, are easy to overlook. Most Americans recognize that they generally do not achieve their stated goal of preventing corruption, nor do they appear to limit the ability of wealthy individuals and corporations to spend as they wish on influencing elections and policy. But the thousands of pages of regulations force candidates to behave in a strictly regimented way that helps explain why campaigns today begin so much earlier than they used to.

And the Citizens United era will lead to shorter campaigns?  Hmmm.