For those that are heartily sick of the 2016 presidential election, there’s some good news. It appears the 2020 race has already started for Republicans. It’s true that we are a little more than eight months away from the November election and that the battle for the GOP nomination is not over. Yet for the political class, there is no respite in the ongoing battle for power. But what ought to trouble Republicans is the idea that some of the calculations two of the leading 2016 contenders are making about the next election may be influencing their decisions about how to conduct themselves now as elements of the GOP fight a rearguard action to try to deny their party’s nomination to Donald Trump.

The context for these calculations is in an uncertain dance, which is what those who are left in the Republican “establishment” are doing with Ted Cruz. Cruz remains the last best hope to stop Trump, and some Congressional veterans that generally despise the Tea Party bomb thrower — like Senator Lindsey Graham — have swallowed hard and endorsed Cruz. But, as the New York Times reports, while it might be in Cruz’s interests to bury the hatchet with people like Senate Majority Leader Mitch McConnell (whom he called a “liar” on the floor of the Senate), the Texas senator isn’t prepared to do so. As a result, some of the people that are most frightened by the prospect of a Trump takeover of the GOP — both because of the policy implications and the prospect that he will lead them to an epic landslide defeat — are keeping him at arm’s length just at the moment that he needs them.

Part of this stems from the genuine antagonism that exists between Cruz and, with few exceptions, the rest of the GOP caucus. But it is also a function of Cruz’s belief that he can’t change his brand merely for the sake of rallying a little extra support for the current race. Though he has issued public calls for a unified struggle against Trump, he doesn’t appear willing to do much if anything to achieve it. The speculation is that he sees himself as Ronald Reagan in 1976, when the future president suffered a narrow defeat in the battle for the GOP nomination but remained true to his conservative beliefs and ultimately prevailed four years later. In other words, though Cruz is still talking about beating Trump now, he knows that if he is to have another try in 2020, he can’t get too close to party power brokers lest he lose his image as the man at war with the establishment.

The same sort of thinking appears to be going on in the Marco Rubio camp. After his withdrawal from the presidential race earlier this month, there was speculation about him endorsing Cruz. A possible Cruz-Rubio unity ticket was even mooted by some in the Cruz camp as a way to bring some of the Florida senator’s establishment backers behind his efforts. But despite some extravagant praise from Cruz directed at his former adversary, Rubio hasn’t endorsed him, let alone agreeing to run as his number two.

The reported reason for this decision is that some of Rubio’s top supporters don’t like Cruz and have urged him to stay away from him. So far, Rubio appears to be listening to them, and the result is that many of his top contributors, as well as many of the activists that backed him, are still refusing to help Cruz stop Trump.

The reason for this is again 2020. Rubio is already looking ahead apparently believing, like Cruz, that the next presidential election will be an open battle for the GOP nod after Donald Trump goes down to an inglorious defeat in 2016. If he’s going to have a chance to do better next time than he did during this election cycle, he can’t afford to alienate his friends. He may also think that playing second fiddle to Cruz in any stop-Trump movement, whether as an ally or a potential running mate, will also diminish him looking ahead to the next go round.

Given the likelihood that Trump will win the nomination this time, it isn’t crazy for both Cruz and Rubio to be thinking ahead. Nor can one say that their calculations are wrong. If Cruz is to have a chance in 2020 he will have to remain a champion of rebellion against the party establishment. If Rubio is to be more than an afterthought next time, he needs to rally his supporters from 2016 as well as bringing in those who might have backed other candidates, and that may not be helped by any formal rapprochement with a potential rival such as Cruz.

Predicting presidential races four years in advance is madness. Yet if, as most Republicans believe, Trump is defeated, that will set both Cruz and Rubio up for another try against a President Hillary Clinton.

But if that is what they are thinking, they need to take a deep breath and think again. It’s not just that any assumptions about 2020 are mere guesses. It’s that if they don’t move heaven and earth to stop Trump, the Republican Party they seek to lead won’t be the same vehicle that can lift either to the presidency.

The trouble here is that Cruz and Rubio, like many in Washington, may be thinking that however strong the Trump surge may be now, it’s a passing fad that will be gone in four years. But while it’s just as silly to try to predict what Trump might do next week as it is to wonder about four years from now, what Republicans need to understand is that if they lose their party now, it won’t be so easy to get it back in 2020. Indeed, it might already be too late to unify a GOP split between pro and anti-Trump Republicans.

The ground is already moving beneath the feet of Republicans as their party stands in danger of ceasing to be the standard bearer for conservatism and is, instead, becoming one hijacked by populist isolationist and protectionist forces. Cruz may think he can out-Trump Trump, but even he may not be isolationist enough for Trump fans. Assuming Trumpism disappears in the dust of a defeat at the hands of Clinton is a risky bet. Both Cruz and Rubio need to understand that if Trump isn’t halted now, it will not go away so easily. Moreover, if Trump forces are able to dominate the Republican convention in Cleveland, it may be the start of the Trumpification of the entire party.

We have no idea what the political landscape will look like in two, three, or even four years from now. But to assume that the next presidential race will look more like 2012 than 2016 is almost certainly a mistake. If Cruz and Rubio want their party to exist as something other than a populist celebrity personality cult, they need to put aside their differences and scruples and devote themselves to beating Trump. Anything else places more than their personal presidential ambitions into jeopardy.