The GOP has an unusual number of potential 2016 presidential candidates who are very young and/or new to the political scene. Each will have to decide whether to make a run or wait for an auspicious time in another cycle. There are a lot of reasons for top-tier candidates not to run.

REFILE - CORRECTING TYPO IN PLANT NAME Texas Governor Rick Perry speaks at the Flextronics plant that will be building the new Motorola smartphone "Moto X" in Fort Worth, Texas September 10, 2013. The factory is a high-profile endorsement for "onshoring" manufacturing in the U.S. REUTERS/Mike Stone (UNITED STATES - Tags: POLITICS BUSINESS TELECOMS INDUSTRIAL EMPLOYMENT) Texas Gov. Rick Perry speaks in Fort Worth. (Mike Stone/Reuters)

Sens. Rand Paul (R-Ky.), Ted Cruz (R-Tex.) and Marco Rubio (R-Fla.) are all freshman, with Paul the oldest (51). The danger for each is that if they go for it and fail, they may cast a shadow on their future prospects, especially if they do poorly. Just ask Texas Gov. Rick Perry. If the slide in the tea party’s fortunes continue, they may find themselves increasingly out of step with mainstream Republicans who have had enough of the shutdown mentality and are looking for a mature executive. Moreover, in 2016 Rubio and Rand Paul will be up for reelection. Do they give up on reelection?

Moreover, to one extent or another, all of these senators have had a rocky year or so. Cruz is still trying to live down the budget debacle of 2013. Paul has stumbled through plagiarism charges, a flap over hiring a pro-Confederate adviser and ongoing battles with Christian conservatives over his isolationist foreign policy. Rubio has managed to confuse and frustrate nearly every element of the GOP, from anti-immigration advocates to business groups (irate over the shutdown he supported) to hawks (who have been exasperated over his inconsistency, most especially on Syria). All of them, frankly, might benefit from a few years of maturation and the passage of time.

At 44, Rep. Paul Ryan (R-Wis.) is also a young man with many more presidential election cycles ahead of him. He’d have to balance the demands of the Ways and Means chairmanship with a presidential run. Does a presidential race distract from or put more focus on his policy agenda? While he personally may prefer to wait (as he did in 2012) if the top gubernatorial contenders (New Jersey’s Chris Christie, former Florida governor Jeb Bush and Wisconsin Gov. Scott Walker) fail to materialize, pressure will be intense from business groups, donors and mainstream Republicans for him to jump into the race.

Then there is Walker, who is gaining attention in part because he has none of the flaws other contenders seem to have: He hasn’t been in the Senate, championed quixotic efforts to shut down the government or bump up against the debt ceiling, been involved in any scandal or offended any contingent of the party. But, as former governor Tim Pawlenty proved, a nice guy and the second choice for most voters doesn’t guarantee success. Walker is certainly a more capable politician than Pawlenty, but it is not yet clear he has the ego, the desire or the team of advisers needed for a presidential run. He will need to spend 2014 getting himself reelected, which (unlike for Christie) will chew into time available for wooing national donors and brushing up on foreign policy. Here, too, Perry is the warning: A successful governor can be a very poor presidential candidate if not adequately prepared and that can permanently mar his reputation. No one really runs for VP, but (as his fellow Wisconsinite Ryan did) Walker might prefer to stay out of the limelight, get reelected, make his way onto a ticket and thereby hop to the front of the line for 2020 or 2024.

At the other end of the spectrum are those pols for whom 2016 is probably do or die. Jeb Bush is 61 and has been out of office since 2007. The current media environment is already a bit beyond his experience. If he is going to run for president, 2016 is likely the best shot he will have, in large part because the reform agenda the Republicans are developing began in large part with him and other proactive Republicans who, for example, championed school choice and reform. That said, many Republicans close to him have the distinct impression he’s already passed the moment when a presidential run was a serious possibility.

And, finally, Christie will likely either get by the bridge scandal and make a serious run, or be undone by it. It is hard to see how he’d take a pass on 2016 (almost certainly because of the bridge scandal) and then come back in future cycles (where he’d be tagged as the guy who couldn’t run in 2016 because of the bridge mess).

As in 2012, there are many impressive Republicans who could run. However, no one should be surprised if a number of the frequently mentioned contenders don’t. Sometimes the smart thing is not to run (ask Perry). Once a candidate takes the plunge, he’s got to be ready for what follows, which is sometimes the widespread perception he’s not ready for primetime.