Sen. Lindsey Graham (R-S.C.), center, greets fellow senator and presidential candidate Sen. Marco Rubio (R-Fla.), left, during a political fundraiser in Boone, Iowa, on June 6. (Jabin Botsford/The Washington Post)

Look at any national poll on the 2016 Republican presidential race, and you will see three to five candidates clumped at the “top” of the field — all winning somewhere between 9 and 14 percent of the vote. It’s fair, given that clumping, to conclude that the race lacks a front-runner.

But there’s a difference between a race without a clear front-runner and a race in which there’s no discernible momentum among the top tier of candidates. And what we have is the latter, not the former.

Sen. Marco Rubio of Florida is the candidate trending up in that top pack. It’s a trajectory he’s been on since he announced his candidacy almost two months ago. Rubio’s charisma, personal story and relative youth have combined to make him the “it” candidate for the GOP at the moment.

Rubio has also been helped by the slippage of his two main rivals for the nomination: Jeb Bush and Wisconsin Gov. Scott Walker.

Former Texas governor Rick Perry is a Republican contender for the White House in 2016. Here's his take on guns, Obamacare and more, in his own words. (Julie Percha/The Washington Post)

Bush, who will finally announce his candidacy this week, weathered a very difficult past seven days — shaking up his campaign staff amid faltering poll numbers and whispers that his fundraising might fall short of its goals for the first six months of the year.

Walker has largely stayed out of the glare of the national media over the past six weeks or so, but his brief appearance on the big stage earlier this year — think “I don’t know” if President Obama is a Christian — wasn’t exactly confidence-inspiring for Republicans looking to see whether he is ready to take the helm.

Beyond that top three, most unaligned Republican strategists we talk to — and there aren’t many, since roughly 200 people are running for the GOP nomination — see a significant drop-off in the likelihood of any of the other candidates winning the nomination.

The most common name we hear as an alternative to the Big Three is Ohio Gov. John Kasich. And that’s certainly possible, but Kasich remains in the very early stages of a candidacy (he’s not announced yet), so we’ll play a bit of wait-and-see for him.

Add it all up and you get Rubio, the youngest member of this massive GOP field, as a first among equals. For now.

Below are the 10 candidates seen as having the best chance of winding up as the GOP nominee. The rankings are determined by polling, conversations with Republican strategists and a pinch of our sense of things.

10. Bobby Jindal. The governor of Louisiana is running: That we (almost) know for sure. The formal announcement is set for June 24 in downtown New Orleans. But Jindal’s standing is his home state is dismal, and there’s very little excitement about him in national GOP circles. His best hope is to hang around the race long enough that voters tire of their other options.

Ohio Gov. John Kasich speaks at an event at the Clark County Republican Party office June 11 in Las Vegas. (John Locher/AP)

9. Rick Perry. The former Texas governor seems genuinely excited about his second run for president. He even ran onstage at a recent event in Iowa. It’s somewhat surprising for a guy who once didn’t really seem that interested in running for president and then, when he did run in 2012, ran a disastrous campaign. But Perry is the longtime governor of a huge state. And American politics loves a second-chance candidate, right?

8. Chris Christie. The New Jersey governor and his team insist they are taking the long view on 2016. No, he isn’t where they want him to be today, but regular people still aren’t paying any attention and won’t be for some time. Christie got some good news last week when the New Jersey state Supreme Court affirmed the legality of his cuts to the state’s public employee pension fund. He’s also staffing up.

7. Mike Huckabee. The former Arkansas governor and 2008 Iowa caucus winner keeps litigating the culture wars — something the larger GOP probably doesn’t want but still speaks to a key audience in the party, particularly in Iowa and South Carolina. Huckabee is the top claimant to the social conservative mantle in the field, and he’s broadly popular in the larger GOP, but we’re still waiting for him to show he’s running the caliber of campaign that can actually win the nomination.

6. Rand Paul. The conventional wisdom among the GOP smart set about the senator from Kentucky has changed completely since the start of 2015. At that time, there was a sense that Paul had a real chance at being the nominee based on his strong base among libertarian-leaning Republicans and his appeal to other, less-vocal GOP constituencies. But the heightened concern within the Republican rank and file about national security and terrorism badly complicates Paul’s noninterventionist views. Even if Paul wins every libertarian vote in the race for the nomination, if he can’t expand beyond that bloc, it won’t be nearly enough.

5. John Kasich. Nobody benefits from Bush’s stumbles as much as the Ohio governor. Both are clearly running for GOP establishment support, and Kasich recently suggested his window is larger if Bush doesn’t run strong. That’s right. But we also have yet to see Kasich really debut on the national scene. And his 2000 presidential campaign was hardly a tour de force, ending shortly after it began.

4. Ted Cruz. Here’s what the senator from Texas has going for him: (1) unquestioned dominance in the tea party lane of the primary, (2) deeply committed supporters and (3) a group of well-funded super PACs backing him. In a very crowded field, that probably means Cruz will be able to stick around for a very long time. But if he ever makes it into a one-on-one fight with any of the people rated higher than him here (Nos. 1-3), it’s still very hard to see him winning that battle.

3. Scott Walker. Walker, as we mentioned above, has kept a low profile these past few months. What Walker does have is momentum in Iowa, where he and his team are — smartly — lavishing time and money. Iowa is a state that Walker probably has to win given that neither New Hampshire nor South Carolina seems like a natural fit for him. At the moment, he’s probably the favorite to do just that.

2. Jeb Bush. Bush’s struggles mask the fact that he’s still very likely to be the best-funded candidate in the field, and he’s broadly liked within the GOP establishment. Put plainly: Republican power brokers aren’t going to desert him until it’s clear that his goose is cooked (or close to it). And there is so, so much time left in the nomination race. At this time in 2008, after all, we were talking about whether Sen. John McCain (Ariz.) was done for.

1. Marco Rubio. Yup.

Aaron Blake contributed to this report.