Generally, are Senators or Governors Busier?

[Mr. Morden]

Senators can be busy if they want to, but they don't really have to be.  That may be part of why sitting governors seem to be a bit less likely to run for president nowadays, and when they do run they enter the race late.  Note how, in 2015, Christie, Jindal, Kasich, and Walker didn't launch their presidential campaigns until June or July, a few months after most of the Senators did.  It's less problematic for a Senator to become a part time Senator, spending much of their day campaigning in Iowa and New Hampshire.