On Friday, The Fix debuted its list of the top 10 contenders for the 2016 GOP presidential nomination.

For most of these politicians, though, running for president in 2016 would be complicated -- specifically, it would be complicated by their day jobs. Just about all of them will either be up for reelection in 2016 or will be in the middle of their terms as governors, which is hardly ideal for launching a presidential campaign.

All four of the senators on our list, for example -- Marco Rubio (Fla.), Rand Paul (Ky.), Rob Portman (Ohio) and John Thune (S.D.) -- are up for reelection in 2016. That means they'll have to discern whether they can still run for reelection while they run for president. Otherwise, they would have to give up their seats.

Sen. Rob Portman (R-Ohio) at the Republican National Convention in Tampa (The Washington Post)

As of now, Ohio's presidential and congressional primaries are both held on the same day in March, which means Portman would have to run in both primaries simultaneously. Ohio law allows for candidates to seek both offices at the same time, but if Portman got primary opposition, it could complicate things.

Paul has more recovery time if he were to run unsuccessfully for the GOP nomination, with Kentucky's state primary being held in May, while Thune would face a June primary and Rubio's would be in August. (All of these dates are subject to change, of course.)

Compounding matters for Portman and Rubio, though, is the fact that they come from swing states where Democrats will be gunning for them. If either faces a potentially tough reelection campaign, it may not be easy to devote all of 2015 and the early months of 2016 to running a national campaign.

Paul and Thune have more leeway, given that they come from red states where they will likely be favored in both the primary and general elections.

Members of Congress have run for both reelection and for the presidency/vice presidency before, the most recent examples being Rep. Paul Ryan (2012), Joe Biden (2008), Joe Lieberman (2000) and Lloyd Bentsen (1988). But all four had been in their seats for many years and had little to be concerned about when it came to their reelection. Portman, Rubio and Paul are all first-term senators who could be targeted.

On the governors' front, the potential 2016 GOP candidates may still be conflicted, though a little less so than the senators.

Our top-ranked governor, Chris Christie, is up for reelection this year and is heavily favored, but that would mean that he needs to ramp up his presidential campaign in the second year of his four-year term.

Louisiana Gov. Bobby Jindal (R) has it better. He comes in just behind Christie at No. 3 on our list, but he will be in his final year of his two terms in 2015. He would likely be out of office by the time the first primary votes are cast.

Ohio Gov. John Kasich (R) is up in 2014, meaning he would have to win what is expected to be a very tough reelection race and then ramp up for the presidential campaign mere months later.

And Indiana Gov. Mike Pence (R) will be up in 2016, which means he would be in the same position as the senators listed above, having to decide whether he can run for president and reelection or choosing between the two.

It's also just plain difficult to run for office as a sitting governor, given how demanding the job is (it's much easier as an incumbent senator). In fact, over the last two decades, only four sitting governors have run for president -- Pete Wilson in 1996, George W. Bush in 2000, Bill Richardson in 2008 and Rick Perry in 2012 -- while many more former governors have run.

The only Republicans on our top 10 who don't have much to worry about when it comes to their day jobs in 2016 are Ryan, who looks to be pretty safe, and Jeb Bush, the only person on the list who isn't currently in office.

Potential 2016 Democratic candidates have much less to be concerned about. Hillary Clinton is out of office; Biden will be in his final years of the vice presidency; both Massachusetts Gov. Deval Patrick and Maryland Gov. Martin O'Malley aren't running for reelection in 2014 and thus will be out of office by early 2015; former Montana governor Brian Schweitzer is out of office; and Sens. Mark Warner (Va.) and Kirsten Gillibrand (N.Y.) aren't up in 2016.

About the only top Democratic contender who would have to worry about his day job would be New York Gov. Andrew Cuomo (D), who is up in 2014 but is so popular that he'll probably breeze to reelection.

The takeaway from all of this? Politicians love job security and prefer to have a fallback plan if they don't win the presidency, and it's best to run for president when you have nothing else to worry about.

And given the complicating factors of their day jobs, Republicans may again struggle to get some of their top potential candidates to run for president.