Mitt Romney tells supporters in a conference call that he will not run for president in 2016. (The Washington Post)

Mitt Romney’s decision not to jump into the 2016 presidential race gives an immediate boost to former Florida governor Jeb Bush’s candidacy, but over time it could have an even greater impact by opening up the nomination contest to some of Bush’s rivals.

Romney’s three-week consideration of a third presidential campaign left the race where it was before he announced his interest in possibly running again. It was wide open before, and it remains wide open now.

But there’s little doubt that Bush will be seen — and targeted — as the obvious front-runner, given his name, his potential fundraising network, his rough standing in some national polls compared with his remaining rivals, and the aggressiveness, skill and speed with which he has moved in this very early stage to assemble a campaign operation.

It will now be Bush’s opportunity to move even more adroitly to consolidate his position. He has shown flashes of readiness as he has moved around the country the past few months, and the spotlight will shine even brighter on him now that Romney is out.

But with that spotlight will come even more scrutiny of the former Florida governor, who has not run a campaign in more than a decade. Just how ready will he be for all that attention?

What Bush has lacked so far is dominance in the polls. A Fox News poll released Thursday showed Romney leading Bush by about 2 to 1 and doing better against former secretary of state Hillary Rodham Clinton, the most prominent Democrat who is assumed to be running, than anyone else in the GOP field. Romney cited that poll on Friday, saying he wasn’t bowing out because he didn’t think he could win the nomination.

In Romney’s absence, Bush should move up in those polls, but his path to the nomination remains anything but clear. He could struggle in Iowa, where social and religious conservatives dominate, unless there are so many more conservative candidates in the race that the constituency splinters and leaves him a wider opening.

No one knows yet just how strong Bush will be in New Hampshire, a state where early handicapping is particularly treacherous and where voters are only too happy to spring a surprise in the final days before their first-in-the-nation primary.

The absence of a Bush-Romney race and narrative, which would have dominated the political discussions and cornered a significant amount of establishment money, now means the GOP more likely will be engaged in a debate about future vs. past, front-runner vs. a field of lesser-known candidates.

There was no particular love between the Bush and Romney camps as the former Massachusetts governor engaged in his deliberations these past few weeks. In his statement to supporters, read during a conference call Friday morning, Romney clearly tipped his hand in the direction of favoring a new generation candidate over the best-known name in the Republican Party.

“I believe that one of our next generation of Republican leaders, one who may not be as well known as I am today, one who has not yet taken their message across the country, one who is just getting started, may well emerge as being better able to defeat the Democrat nominee,” Romney said. He later added, “I do not want to make it more difficult for someone else to emerge who may have a better chance of becoming that president.”

Perhaps he was talking about New Jersey Gov. Chris Christie. It was widely assumed that Christie was the most damaged by the possibility of both Bush and Romney running, if for no other reason than that all three would have been seeking establishment money to fund their campaigns and roughly the same pool of voters to deliver the nomination.

Until Friday, Christie advisers tried to offer reasons why having both Romney and Bush in the race could be beneficial, at least in the short term (the two bigger names would leave Christie freer of early criticism and allow him to build his campaign slightly in the shadows rather than being targeted by Democrats and some Republicans). But that was distinctly a minority view within the party. Romney out is clearly good for Christie, if he can do something with it.

Christie and Romney long have been friends and allies, even if some of Romney’s supporters had trouble forgiving Christie for embracing President Obama during hurricane relief appearances in the week before the 2012 election. Romney and Christie were scheduled to have dinner Friday night in New York. Perhaps that was an accident of timing or possibly a signal to Romney’s network of donors and advisers of where they should go now.

Romney’s statement about giving lesser-known candidates room to emerge seemed aimed not only at Bush (though Bush has never run for president before) but also at those who have run previously, whether former Texas governor Rick Perry, former Arkansas governor Mike Huckabee or former Pennsylvania senator Rick Santorum.

The space Romney’s departure creates, however, can be a mixed blessing for the others now moving toward running. Had this been a Romney-Bush contest in the coming months, other, lesser-known candidates could have emerged more slowly. Now they, too, will be in the spotlight.

That will be true for Christie, Wisconsin Gov. Scott Walker (whose stock has risen after a well-received speech in Iowa last weekend), Louisiana Gov. Bobby Jindal, businesswoman Carly Fiorina and Sens. Marco Rubio (Fla.), Rand Paul (Ky.), Ted Cruz (Tex.) and Lindsey O. Graham (S.C.), who continues to say he, too, wants to run.

They will now be compared favorably or unfavorably to Bush, in terms of readiness, message, ability to raise large amounts of money and skills as a candidate. But the ultimate question for all of them, from Bush to the rest of the field, will be whether they are seen as capable of defeating Clinton in a general election.

Republicans will have clear choices, both ideologically and in terms of presidential readiness. They are hungry to win the White House, and many in the base are hungry for a true conservative to lead them in 2016. Whoever finds the way to demonstrate both of those qualities will have the advantage. For now, it’s an opportunity for all to try to seize.