Forecasters give Trump and affiliated groups a 44 percent probability of spending between $250 million and $500 million. They give him a slightly lower probability of spending $500 to $750 million. To put that in perspective, Romney and affiliated groups spent $1.25 billion.

In fact, there is a significant chance that Trump could end up spending less than John McCain did in 2008, even though McCain accepted public financing and was limited to only $84 million worth of spending in the fall campaign and even though in 2008 super PACs weren’t able to raise as much as they do now.

McCain’s total haul in the 2008 cycle was about $368 million. That translates to $412 million in current dollars. Could Trump end up raising less? We did not ask the forecasters to make a precise prediction, but if there’s a 44 percent chance that Trump will raise between $250 million and $500 million, then there is certainly a real chance that he raises less than $412 million.