Why is Ben Carson still in the running to become the next US president?

On 23 February, we saw one of the oddest incidents in the bizarre presidential campaign of Ben Carson. The candidate claimed in an interview that if elected he'd be the first true African-American president, as Obama was "raised white".

It's not clear what he's trying to achieve with these comments, they seem unlikely to sway even the most extreme Republican voters. It's possible they are part of a deliberate strategy to provoke controversy for press coverage, following the blueprint of Donald Trump, but maybe he simply has no idea what he's doing.

That he is still in the race at all is something of a puzzle. Floundering at low single digits in the national polls, he has performed poorly in the primaries up to now, and seems to have almost no chance of regaining any ground. This is made all the more confusing by Carson's lack of obvious appeal as a candidate. He surged in the polls at the tail end of last year but faded under quickly under the spotlight.

While he was clearly a highly intelligent and capable surgeon, as a politician he is so laid-back he's horizontal, seeming slow, ignorant of basic facts, and often confused, as in his bizarre stage fright moment a couple of weeks ago. This is above and beyond the usual snide British remarks about American conservatives being stupid. Jeb Bush, Chris Christie and Carly Fiorina all dropped out after outperforming Carson, and yet his campaign trundles on going nowhere in particular.

The answer to this question may lie in campaign finance. Since the Citizens United Supreme Court case, there has been more money in presidential elections than ever before. It is easy to overstate this, the US still spends more money in a year on toilet roll than it does on campaign spending but for consultants and PR people, there is a good living to be made.

The Carson campaign has raised a lot of money, around $68m in total. This is the third most of any Republican candidate and the most if we only consider the campaigns proper, rather than their super PACs. This isn't just a leftover from when he was riding high in the polls, either, in the fortnight after Iowa they raked in another $6m. He clearly has a small but very generous base of support. This translates into spending more than double the amount per vote of the next worst campaign (Jeb Bush, unsurprisingly).

Suppose I'm a powerful, amoral political consultant. I'm looking for a campaign to fuel my money addiction. I could simply steal all the candidate's cash, and do a terrible job of running the campaign, but then I'd probably be arrested for fraud, or the campaign would collapse, so I'd have killed the goose that lays the golden eggs.

Instead I want the campaign to remain as stable as possible, plodding along, raising lots of money and paying off my mortgage. It doesn't really matter how we're doing in the polls, we can keep losing forever as long as the cash keeps coming in.

The one thing I can't let happen is the candidate throwing in the towel. A zombie campaign that only exists to fuel itself with money is all well and good but it is undignified for the candidate.

This is why Jeb Bush, and to a lesser extent Carly Fiorina, Chris Christie and Rand Paul, dropped out. They cared about winning the presidency but once it was over, they had better things to do with their time. If they're going to be a loser, they may as well be a gallant one and not prolong the inevitable. Ben Carson, on the other hand, doesn't seem to care much about this, he was never really a serious candidate, and is doing quite well out of it himself by selling lots of books.

None of this is necessarily a conscious or malicious decision, everyone is just following their incentives. Carson's staff will naturally want to keep the gravy train running as long as possible, so will never voluntarily give up the ghost. Carson doesn't seem like the most politically astute man and seems perhaps more motivated by fame than by power, both of which would explain his increasingly bizarre public statements such as comparing same-sex marriage to bestiality or believing Egyptian pyramids were grain stores, not pharaohs' tombs.

It's even possible that in spite of all evidence, he really does think he's in it to win it and there's no reason for his campaign staff to persuade him otherwise. If this is the case, we could easily see them stringing him along all the way to the convention, dragging his handful of delegates, 5% of the vote and 15 minutes of fame with him.