Politics is never static. Someone who is up one day is down the next. Yesterday’s goat is today’s comeback kid. We’re seeing some of this in the lead-up to the GOP presidential primary.

New Jersey Gov. Chris Christie. ( John Gress/Reuters)

On the upswing, New Jersey Gov. Chris Christie’s approval numbers at home have stabilized. In New Hampshire the most recent WMUR/UNH poll has him leading the pack at 19 percent, up from 9 percent in January, when the bridge scandal broke. He’s also set a fundraising record for the Republican Governors Association.

This is not to say Christie is “ahead” in New Hampshire, and certainly not the “favorite.” But it does suggest that the bridge scandal may not be an impediment to him beginning a presidential run. Whether he decides to run and whether he can win in New Hampshire and elsewhere depend on what kind of campaign he runs, who runs against him and how events play out in New Jersey.

The real wild card remains Jeb Bush. Despite howls from anti-immigration and anti-school standard right-wingers, his popularity has steadily built (from 3 to 7 to 11 percent in the WMUR/UNH poll). Nationally he remains at or near the top of the field. Like Christie, Bush does not to seem weighted down by any disqualifying factor (in his case, his last name). And like Christie, whether he decides to run and, if so, how well he does depends on himself, his opponents and world events.

By contrast, despite his near-constant presence in free media, there has been no Sen. Rand Paul (R-Ky.) breakout. Nor has Sen. Ted Cruz (R-Tex.) or Wisconsin Gov. Scott Walker moved out of single digits. If one or more of them decides to run, they’ll have their chance to prove themselves, but a risk-taking candidate will have to bet on wider support and a bigger donor base coming later.

There are several takeaways from all this. First, no GOP candidate has as much baggage as Hillary Clinton — and several have a better political radar. Second, the incentive for marginal candidates to get into the race remains high if, say, a  15-20 percent share of the vote in a small early primary state can propel them into the top tier. Moreover, with Hillary Clinton now viewed as a vulnerable opponent, some Republicans may decide it’s not necessary to have a veteran or big star to win back the White House. A good candidate with a good message may suffice. Third, world events will put a premium on foreign policy credibility. The quickest way to fall out of serious contention is to be uninformed or irresponsible (or both) on the subject; a quick way to get one’s footing is to show a grasp of detail and a larger national security vision. Finally, although the primary season has been tightened up and the convention will come earlier in the calendar year, this is still a marathon process. A candidate’s self-discipline, money and message have to hold up for weeks and months. Those without a high-caliber, presidential-ready team will be hugely disadvantaged.

In short, the polls tell us what isn’t happening — no breakthrough candidate, no disqualifying conditions for the big-name contenders. A year and a half before the first Iowa caucus gathering, it is impossible to predict who will be in the race, let alone who will win. But if you’re a respected Republican, understand foreign policy and have a compelling contrast to the Obama-Clinton-John Kerry train wreck, and have even a smidgen of executive experience, why not run?