In 2016, by contrast, there's a glut of sitting governors whose names have been floated, including Chris Christie, Scott Walker, John Kasich, Bobby Jindal, and Mike Pence. They will all have to balance their national political ambitions with their states' political realities.
David Contarino, a Democratic strategist and Richardson's 2008 presidential campaign manager, said the calculus for announcing a presidential bid is different for governors because, unlike other politicians, they have to work within the parameters of their state's legislative session. The process of passing a state budget, for instance, can extend into the summer, depending on the state.
"Most governors, I would think—particularly those just coming off reelection—would want to get through some or all of their legislative session and maybe chalk up some victories there that they could point to," Contarino said.
Yes, governors with presidential ambitions can be hampered by the timeline of the legislative session, but they also benefit by having executive credentials that are more akin to a president's responsibilities.
"There's no question that governors, in that regard, have more constraints on their time than current or former legislators," Pawlenty said. "But it also comes with some advantages."
If you're a senator...
Senators have a distinct fundraising advantage early on in the primaries. That's because, as members of an elite governing body, many of them have built-in national name recognition. It also means that they are freer to fly around the country, courting donors. Since the beginning of 2013, Sens. Rand Paul and Ted Cruz have traveled to the first three primary states of 2016 a total of 15 and 16 times, respectively.
"They have some more freedom and flexibility to get around," Contarino said. "Senators have more of a national audience because they're dealing with federal issues, whereas a governor can often be mostly restricted to the issues that are dealing with in his home state."
That name ID means senators can afford to take more time announcing their bid. However, the behind-the-scenes work of building a campaign is already happening. Aside from courting donors, candidates also need to poach sundry consultants, fundraisers, and on-the-ground staff in early-primary states like Iowa before their competitors do—something that Sen. Rand Paul and Gov. Martin O'Malley are already working on.
The political downside to campaigning is missing some Senate votes. Because of his two presidential campaigns, Sen. John McCain has the second-worst attendance record in the Senate. The upside: Vote attendance isn't necessarily something the average voter pays attention to.
If you want to get out in front early...
The schedule of different state primaries can also affect how early candidates start announcing. In 2008, Iowa and New Hampshire's primaries were scheduled at the very beginning of the year, which led Democratic primary candidates to push their announcements way to the front.