5 Ways Jeb Bush's 2016 Announcement Will Shift the Presidential Landscape

— -- Jeb Bush’s announcement this morning that he will “explore the possibility of running for president of the United States” has shaken up the 2016 landscape, making him not only the first Republican candidate to make such a move, and by far the biggest name, but also sends a clear message to donors to stay put.

Here are five ways the former Florida governor’s 2016 announcement will shift the presidential landscape.

1. Jeb Bush May Be an Early Front-Runner, Leads in Poll, but Still Work to Do

Just a few months ago, many thought Bush wouldn’t make this move, but today’s announcement not only makes him the first one in, but also makes him the GOP front-runner, although polls show he still has much work to do, as do all of his possible rivals. In a new ABC News-Washington Post poll out today, Bush comes in first, but with only 14 percent of Republicans and Republican-leaning independents who are registered. In a match up without Mitt Romney, Bush is first, with Paul Ryan next with 11 percent support, Rand Paul with 10 percent, and six others have 7 or 8 percent apiece. He may be on top, but that means 86 percent of leaned Republicans aren’t Bush backers. Bush has major name recognition, which is clearly helping him in this poll.

The best news out of the survey for Bush is that he comes in first with “mainline Republicans” and those are the voters most likely to participate in the primary process. With those voters he has 19 percent, while Ryan has 14 percent. But Bush is not first with GOP-leaning independents. Instead, Paul has 15 percent with that group, Christie has 10 percent, while Bush has 9 percent.

If Romney does get in, he comes in with 21 percent support while Bush has 10 percent, and 9 percent for Paul and 8 percent for Ryan.

2. Who Might Stay Out?A Bush aide cautions that this move isn’t even an exploratory committee yet. Instead, Bush is making a first move to set up a leadership PAC to “engage politically in a more focused way,” but the aide notes Bush has “not made a final decision on whether he will run. He will now “actively … get out there to gauge his support” with both donors and voters, according to the aide.

His decision process will likely grab a great deal of establishment support within the Republican Party and throws a wrench in their possible plans, and limits the appeal of other candidates who could grab that establishment support, including Mitt Romney, Chris Christie and possibly Marco Rubio, the Florida senator and friend of Bush’s. Rubio spokesman Alex Conant told ABC News Rubio won’t make his decision based on Bush’s news.

"Marco has a lot of respect for Governor Bush, and believes he would be a formidable candidate,” Conant said. "However, Marco's decision on whether to run for president or re-election will be based on where he can best achieve his agenda to restore the American Dream -- not on who else might be running."

In 2016, Rubio will also be up for re-election. He has said he wouldn’t run for both the nation’s top office and his Senate seat. Romney has said he’s not running, but recently the buzz that he could make a third run is back. Bush’s likely entry would mean an establishment choice that likely likely limits the voter appetite for a Romney candidacy.