Donald Trump still remains atop the New Hampshire leaderboard in a new poll from Boston’s WBUR, but another candidate seems to have caught some momentum in the Granite State, too. Chris Christie more than doubled his support in three weeks, climbing to a tie for second place with Marco Rubio, 27/11/11. When counting leaners, Christie edges Rubio, 27/12/11:

Christie’s support has doubled since WBUR’s November poll, to 12 percent — which vaults him into second place, just ahead of Rubio at 11 percent. Texas Sen. Ted Cruz maintains a position in the second tier as well with 10 percent support, signaling a three-way race for runner-up.

Trump picked up four points when counting leaners from the previous poll, which means that his comments about barring Muslims from entering the US didn’t hurt him in New Hampshire, and may have given him a boost. Rubio dropped two points among leaners but otherwise is in roughly the same position as in the last two iterations of this polling series. Cruz has risen slightly over the same period of time, offering a trio of options to Trump for Republican voters.

If all of those candidates are gaining, then someone’s losing — and that would be Ben Carson. Six weeks ago, Carson was unchallenged for second place with 16% and was within the margin of error to Trump’s 18%. Carson has now dropped to 6% into seventh place, below both Jeb Bush (8%) and John Kasich (7%). Kasich has slipped from a fourth-place 10% at the beginning of November to single digits now, which doesn’t give Ohio’s governor much reason to hope for a breakout.

For Christie, though, New Hampshire holds more promise. Its relatively close proximity to New Jersey gives Christie more visibility and familiarity than Rubio, Cruz, Bush, or anyone other than Trump. If Trump’s bombast sells, then Christie can offer some of his own, tempered with a more pragmatic approach and policy chops, which matter to New Hampshire voters in the end.

CNN notes that a key endorsement for Christie might have contributed to his uptick:

But New Jersey Governor Christie has surged into second place at 12% on the back of an endorsement from the New Hampshire Union Leader newspaper and a singular focus on campaigning in the first primary state.

Meanwhile, support for retired neurosurgeon Ben Carson is in free-fall, registering just 6%, down 7 points from a WBUR poll in mid-November. The slide comes as Carson’s campaign has struggled with foreign policy and media scrutiny.

All that does is give Christie an opportunity to build on the sudden momentum. The Union-Leader endorsement spike won’t last long unless Christie can convert it into real growth in support. He’s still at less than half of the support that Trump has, too, and there isn’t really a lot of upside for finishing second in New Hampshire unless one wins South Carolina, and Trump owns that state. The trailing trio will have to figure out how to out-vault each other and catch up to Trump pretty quickly, as the voting takes place in less than nine weeks. It might be (past) time for everyone else to look for something else to do.