Former Florida governor Jeb Bush (R) walks to the podium to speak at the Washington Marriott Wardman Park Hotel in Washington, D.C., on Nov. 20. Bush was the opening speaker at the 2014 National Summit on Education Reform conference. (Mark Wilson/Getty Images)

Jeb Bush became the first big-name potential GOP presidential candidate to make a major 2016-related announcement Tuesday, announcing that he will "actively explore" a run.

Generally, this kind of announcement will be accompanied by an "exploratory committee" — which is both legally and practically the same thing as launching a campaign, and is usually just an excuse to have two separate campaign announcements.

The former Florida governor isn't quite going that far; he says he will launch a new leadership PAC in January instead.

But make no mistake: Bush just sent a clear signal that he's very serious about running for president in 2016 (in case that wasn't already clear) and will very likely take the plunge. And his decision to announce this in December 2014 places the onus on all the other GOP candidates to get their ducks in a row — in a hurry.

The reason? The 2016 GOP primary is set to be the most wide-open contest we've seen in a very long time. A new Monmouth University poll of the GOP field released as Bush was making his announcement showed no candidate getting more than 10 percent of the vote (the poll was open-ended).

The early maneuvering in a presidential campaign is all about securing the staff, donors and big-name support that you will need going forward. And the moment that a big hitter like Bush starts actively and publicly engaging in that process, others will start feeling antsy about letting him get a head start.

Does that mean that a bunch of GOP candidates will start announcing for president before the New Year's? Probably not.

But there are lots and lots of potential candidates and a limited number of the best people and money to help them become the next president — especially for establishment-oriented candidates like Bush. Bush has signaled that he's likely to be one of their options to support in 2016, and we should expect others to make similar signals — if not launching actual campaigns — in the weeks ahead.

People like Chris Christie, Marco Rubio, Scott Walker, Bobby Jindal and even Mitt Romney would be competing for the same people as Bush. Those people will want to know what the candidates' plans are or if they can back Bush.

The 2012 GOP primary got started somewhat slowly because there was an established front-runner (Romney) and relatively few candidates who were actually competing for that internal base of establishment support. And if GOP leaders had their druthers, they'd probably prefer this one didn't get started until the spring. It's more time for in-fighting and draining party resources, after all.

But that probably wasn't a realistic hope.

Former Florida governor Jeb Bush told fall 2014 graduates "no matter what path you choose, don't let anyone else ever tell you how big to dream." (University of South Carolina)