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Updated to reflect new information about Ben Carson's campaign.

As of Friday, the number of Republican presidential candidates stands at 10 and counting. It's a number that's certain to grow in the coming weeks with the expected official entrances of former Florida Gov. Jeb Bush, Louisiana Gov. Bobby Jindal and, yes, even Donald Trump.

At this point, the better question might be who isn't going to run. Ohio Gov. John Kasich sure sounded like a likely candidate in an interview with NPR's Don Gonyea this week in Iowa. And Wisconsin Gov. Scott Walker is all-but-in.

That leaves Chris Christie as the only question mark on the GOP side. The New Jersey governor probably wishes he had a time machine to go back to 2012, when he was atop the polls and seen as the biggest threat to eventual nominee Mitt Romney. But Christie passed, casting an eye toward 2016 instead. Now, four years later, his poll numbers have sunk, and he's embroiled in scandal. Christie is still making noise with town halls this week in New Hampshire and Iowa – the format where he excels most – but he he's nowhere near the top tier anymore.

Caution ahead for Carson. There was one reason revealed this week why the field might be so crowded — running for president can improve candidates' personal financial stock. The Wall Street Journal calculated that retired neurosurgeon Ben Carson and his wife earned between $8.9 million and $27 million in the 16 months since he began dipping his toe in the presidential waters — from speeches, books and corporate boards. In 2008, former Gov. Mike Huckabee parlayed his second-place finish into a lucrative Fox News contract, as did many other former rivals. If you're wondering why people like former New York Gov. George Pataki are running – yes, they have policy and ideas they want to push, but it also makes them relevant again. One cautionary tale, however: The 2012 presidential campaign didn't help Newt Gingrich. His Gingrich Group LLC, where the majority of his wealth was tied up, filed for bankruptcy in April 2012.

But there are major warning signs ahead for Carson. The Washington Post reported late Friday that four of his senior campaign officials have bolted in recent weeks and super PACs backing his campaign are also in turmoil. Carson is a political neophyte, and as appealing as an anti-Washington, anti-politician message is, inexperience shows in presidential campaigns without seasoned veterans pulling the strings.

Rick Perry's promise. Another candidate who is hoping for another shot at relevance is former Texas Gov. Rick Perry. Perhaps no candidate has more to prove than Perry in 2016. The Texas governor entered the 2012 presidential race with great fanfare – then quickly flamed out. His infamous "oops" summed up his floundering campaign, but in reality his fate in the race had been sealed long before that. As we wrote last week in Iowa, Perry appears to be a changed man on the campaign trail – he's full of energy and sports a new look (though his wife, Anita, insists the glasses were necessary). And he just got a big get in Iowa with the endorsement of influential Iowa conservative radio host and activist Sam Clovis. Clovis backed former Pennsylvania Sen. Rick Santorum in 2012, who went on to narrowly win Iowa that year. It is a notable loss, however, for Santorum in this more crowded field. State observers say to watch Perry over the next few weeks – he's building a good team in Iowa. And though his poll numbers don't reflect momentum yet, he has the potential to make a big surprise.

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