Dr. Ben Carson, left, exits after speaking during the Leadership Forum at the 144th National Rifle Association (NRA) Annual Meetings and Exhibits at the Music City Center in Nashville, Tennessee, U.S., on Friday, April 10, 2015. Top Republican contenders for their party's 2016 presidential nomination are lining up to speak at the annual NRA event, except New Jersey Governor Chris Christie and Kentucky Senator Rand Paul who were snubbed by the country's largest and most powerful gun lobby. Photographer: Daniel Acker/Bloomberg *** Local Caption *** Ben Carson

The big news* Monday morning: A new poll of the 2016 Republican presidential primary shows renowned pediatric neurosurgeon Ben Carson in the lead*! At 11 percent!

Carson, you might recall from reading The Washington Post last week, is running a campaign beset by problems including a staff exodus. And he just grabbed the lead*.

It's one of the many wonders of the hugely wide-open Republican presidential primary. In releasing the poll, Monmouth University made an interesting case: That the GOP presidential race essentially has no top tier; it's all just a cluster of candidates at this point.

“You would be hard-pressed to look at these results and identify an emerging top tier in the Republican field, let alone a so-called frontrunner,” said Patrick Murray, director of the Monmouth University Polling Institute.

That's kind of true -- at least if you're only looking at polling. There are many other considerations here, including the ability of the candidates to raise money for and run a national campaign, which most (we'd argue) lower-tier candidates (like Carson) will struggle to do. This is why The Fix Boss and I have identified what is basically a three-candidate top tier of Jeb Bush, Marco Rubio and Scott Walker right now.

[The GOP field: We made a top 10 list, but really, at this point, it’s just three]

But that top tier isn't borne out in the polling right now -- at all. In fact, all three are statistically tied with the likes of Carson and even Mike Huckabee for the lead.

What's perhaps most remarkable is that the leader is at just 11 percent. That's basically unheard-of in modern polling. When we wrote a little more than a year ago that the GOP primary was likely to be the most wide-open contest ever, the leaders were at 13 percent; today's they're as low as 10 percent (in a recent Fox News poll) and seem destined to drop into the single digits as the field keeps ballooning.

A year ago, nine candidates were within seven points of one another; today eight candidates are within seven points of the erstwhile leader*, Carson.

Sure, names like Bush and Walker momentarily took over at the top spot at various points this year. But today, it's just a mess of names that tells us almost nothing, with the leader of the field taking an ever-decreasing share of the overall vote.

Here's a look at how much of the vote the leader of the Republican primary has taken over the past six months:

As we noted last year, it's hugely unusual to have a race that basically has no frontrunner or group of frontrunners. There's really no recent precedent for a race that polls as wide-open as this one does.

In 2012, virtually every early poll had Mitt Romney as the clear front-runner, often by double digits. In 2008, John McCain led in every national poll until November 2007. In 2000, George W. Bush was the clear and early front-runner two and half years out. The same was true in 1996 for Bob Dole and in 1988 for George H.W. Bush, in 1980 for Ronald Reagan and in 1976 for Gerald Ford.

All of which kind of obscures the fact that there are relatively few candidates with the demonstrated ability to run the kind of campaign it takes to win. Even those candidates, though, are going to have to navigate a massive field of contenders that renders strategically positioning yourself in relation to other candidates much more difficult. And given we simply haven't seen a race that's this wide open, we can't really say with certainty that the money and organizational advantages that usually reign supreme are as hugely important as they used to be.

After all, in a field where the leader is at 11 percent right now and in a state like Iowa where the winner took less than 25 percent of the vote in 2012, it's not inconceivable the winner this year could be stuck in the teens. And who's to say that couldn't be Carson?

* Not really