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

Mitt Romney told supporters Friday morning that he won’t pursue a third run for president in 2016. It was a major surprise given that, since he made his interest in the race known three weeks ago, he had given every sign he was moving closer to the race, not further from it.

“After putting considerable thought into making another run for president, I’ve decided it is best to give other leaders in the Party the opportunity to become our next nominee,” Romney told his finance committee on a conference call Friday, according to a copy of the remarks obtained by conservative talk show host Hugh Hewitt. “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.”

That second sentence is key to not only understanding Romney’s thinking about his own candidacy (or lack thereof) but also how he feels about the race more generally. His motivation to reconsider his past denials of interest in a third race seemed designed to slow the momentum being built by former Florida governor Jeb Bush. The two men have a testy relationship, and Romney has made clear privately and in kinder terms publicly that he didn’t think Jeb was the right choice for the party.

Romney’s consideration of the race over the intervening three weeks was entirely tied up with Bush and his own plans. It was huge news — in the political world — when, on Thursday, Dave Kochel, a longtime Romney adviser, signed on with Bush to be his campaign manager. The entire conversation over the past 21 days was whether, with Jeb and Mitt in the race, there would be room for any of the “new” faces in the party such as Wisconsin Gov. Scott Walker or Florida Sen. Marco Rubio (or even New Jersey Gov. Chris Christie).

Romney knows — and wants to make sure anyone who reads or hears his statement knows — that elections, especially ones for president, tend to be about the future, not the past. (As I wrote soon after Romney started to consider running again, his past — 47 percent etc. — would never have allowed him to make his 2016 race about the future.)

Now, with Romney out, the dynamic of the race will be fundamentally altered. The choice is now likely be generational in nature. Bush, at 61, will be nearly a decade older than any of his serious competition in the race. (Christie and Kentucky Sen. Rand Paul are both 52.) And, he will be almost 20 years older than people such as Rubio, 43, and Texas Sen. Ted Cruz, 44. (To be clear: The age difference won’t be the only issue at play now in the Republican primary. But it will absolutely take on greater significance with Romney not only out but also highlighting it in his decision not to run.)

The generational question will be even more important because of the increasing likelihood that Hillary Clinton will not be seriously challenged for the Democratic nomination. At 67, Clinton would be among the oldest people — in either party — to win a presidential nomination. And Romney — and lots of other Republicans — clearly feel as though the best (only?) way to beat Clinton is to nominate a fresh-faced Republican who can paint Clinton as a figure of a past that is better forgotten.

Call it the Reverse Obama: A key to then-Sen. Barack Obama’s message in 2008 was that he wasn’t part of the old way of doing things. His age — and relative newness to the national political landscape — helped affirm that message and was critical to his toppling of Clinton in the primary and his sound defeat of John McCain — age 72 at the time — in the general election.

That age contrast — both in a primary and a general election — seems to be what Romney really wants. How much of that is about his personal distaste for Bush and how much is genuinely tied into a belief that it’s time for the party to move on is very, very difficult to know. But regardless of his motivation, Mitt Romney is going to get the primary race he wanted in 2016. All it took was for him to decide not to run.