If you, like us here at FiveThirtyEight, were initially skeptical of Donald Trump’s chances of winning the GOP nomination in part because you assumed that the Republican Party would go out of its way to stop him, then you’ll find the following pretty remarkable. According to Tim Alberta of the National Review, there are currently no negative television ads running against Trump in Iowa, New Hampshire or South Carolina.

There are a lot of reasons for this — including, paradoxically, both resignation to the idea of Trump as the nominee, and conversely, a belief that Trump’s support in national polls won’t translate into winning margins in Iowa and other early voting states. But there’s another dimension to the problem too. It should have been perfectly obvious, but it became clearer to me after spending the past week in Iowa: The campaigns competing against Trump are acting in their own narrow best interests, and not necessarily in the best interest of the Republican Party.

If you look at the race through the lens of the national media, it’s easy to focus solely on Trump, and to a lesser extent Ted Cruz and Marco Rubio. But in Iowa, there are a lot of other Republican campaigns too. Some, like Ben Carson’s, are relatively visible in the form of billboards and advertisements. Others, like Rick Santorum’s, you really have to go looking for. All of these campaigns still have boots on the ground. However implausible their candidate’s chances might be, it’s the job of their staffers to keep working for their candidate until the bitter end.

So unless the Republican National Committee itself were to buy airtime to run negative ads against Trump, the question is which individual candidates might benefit from doing so. This answer is more complicated than you might think.

The most important part of the calculation is that if Trump doesn’t win Iowa, Cruz very probably will instead. In fact, if Trump slumps during the final two weeks of the campaign, Cruz could win resoundingly in Iowa, since polls suggest that he’s the second choice of many Trump voters.

So what would the other candidates rather have: an overwhelming Cruz win in Iowa or a close finish between Cruz and Trump?

Rubio, for example, might prefer a close finish. For one thing, if Cruz and Trump almost evenly split their vote, there’s an outside chance that Rubio could win Iowa himself with something like the 25 percent of the vote Mitt Romney got in 2012. Furthermore, a big Cruz win in Iowa, coupled with a big Trump loss, might be enough for Cruz to surge to the top of New Hampshire polls and win there too.

What about Chris Christie? Christie’s tough-guy persona might seem perfect for taking on Trump, especially during a debate. But Christie, like Rubio, has largely avoided confronting Trump. That too could reflect a strategic calculation. To win the nomination, Christie will first need a good performance in New Hampshire. Then he’ll hope to survive until the latter half of the nomination process, when lots of delegate-rich (and often winner-take-all or winner-take-most) blue and purple states vote. He’s playing a long game, in other words, and he might not mind some Trump-induced chaos in the short run if it prevents Cruz or some other candidate from slingshotting to victory.

Obviously, the calculations that Rubio and Christie are making may be wrong. Jeb Bush and John Kasich, whose situations are not all that different than Christie’s or Rubio’s, have chosen to attack Trump instead. Furthermore, the more Trump becomes a threat to win the nomination himself, instead of being a bumper that other candidates try to ricochet against, the more urgent it becomes to attack him.

That may be what Cruz’s campaign has figured out. After months of buddying up to Trump, Cruz is now shifting into attack mode. While Cruz might prefer a cordial victory over Trump in Iowa, maintaining a favorable image with Trump supporters so as to convert them into his camp later on, Trump remains too much of a threat too late in the race for Cruz to feel assured of that now.

It might seem ironic that the establishment could soon be counting on Cruz to save itself from Trump. (Cue the scene from “Jurassic World” when T. Rex is summoned out of its cage to battle Indominus Rex to the death.) But if you consider the problem from the standpoint of the individual campaigns, and not “the party” as a whole, it makes a lot more sense.

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