His campaign started out stuffed with money.

By last July, Jeb Bush had raised $103 million for his super PAC, Right to Rise, an astonishing sum that seemed to foretell the most lavishly funded campaign in American history. No super PAC had ever raised so much cash so early in an election cycle. In fact, Right to Rise alone outraised all the super PACs combined at the same stage in the 2012 elections.

Now, after primary elections in just three states, Bush is out. He finished sixth in the Iowa caucus, fourth in the New Hampshire primary, and now, fourth in the South Carolina primary. It has become a given in modern American politics that money buys results, but Bush's rapid flameout suggests a more nuanced reality: Money can buy an edge, but successful candidates still need broad-based support and lots of smaller donors.

Bush‘s strategy from the beginning was to lure wealthy donors able to write six- and seven-figure checks to his super PAC. But his campaign itself was never well-funded, and that turned out to be a critical gap. Super PACs, which can accept unlimited amounts of money, can pay for ads and other types of advocacy—either for the favored candidate or against rivals—but they’re not allowed to cover basic campaign expenses such as salaries for staff, travel costs, event fees and anything else done by the campaign proper. That's what the presidential campaign committee is for, and that's limited to maximum donations of $2,700 per person for the primary elections, and another $2,700 for the general election. So even with a gargantuan super PAC, it's still crucial to have a lot of donors funding the traditional campaign.

Here are fundraising totals for the major candidates, which clearly show Bush’s disadvantage. These are for the full year of 2015, the latest comprehensive figures available:

While Bush was tied with Democrat Hillary Clinton for the most money raised through a campaign committee and a super PAC combined, he ranked sixth in money raised by the campaign alone. Given that billionaire Donald Trump is funding his own campaign and has pledged to spend at least $100 million if needed, Bush effectively ranked seventh in campaign funding. Except for John Kasich, all of the candidates with less money have now dropped out.

Bush also burned through money faster than some of the other candidates, and spent more overall, as this table shows:

Had Bush performed well in either Iowa or New Hampshire, his fundraising may have picked up in 2016. Instead, the opposite happened. Bush's poor showing strengthened Donald Trump, Ted Cruz and to a lesser extent Marco Rubio and John Kasich, all of them gaining momentum at Bush's expense. Rubio, who also has a high burn rate, is positioned to benefit from Bush's departure, since he may get many of the "establishment" donors Bush supposedly had locked up. Meanwhile, Ben Carson's days seem numbered, since he hasn't done well anywhere in actual voting.