One of the big problems facing the GOP is that it is making enemies fast. Furthermore, Trump relies almost entirely on fear and greed to hold onto power. When that works, it works. But the moment his threats prove hollow and his promises are no longer credible, many of his elite level supporters will turn on him in an instant and disavow him as quickly as he has disavowed a huge share of his minions.
Also, now that Trump has delivered on creating an ultra-conservative U.S. Supreme Court (both due to their abortion politics and for other reasons) and permanent tax cuts for the rich, many supporters who collectively held their noses to back him predominantly for those reasons, no longer need to support him.
* First and foremost, the Roman Catholic Church has started to seriously mobilize against their anti-immigration efforts. They have picked a fight with the largest religious denomination in the nation, led by a Pope who understands American politics at an intuitive level, which includes an important share of their base and of their elites. While White Evangelicals are realistically going to continue to be Trump and the GOP's do or die supporters, they need the political support of conservative white and Hispanic Catholics as well to secure majorities.
So far, the Catholic Church in the U.S. has only taken some baby steps to accommodate a heavily immigrant group of parishioners. But the Pope has an immense capacity to turn up the heat, and Trump has denied himself a key tool to fight that by having the IRS take the position that churches can endorse candidates in our elections from the pulpit.
What happens if Catholic justices on the U.S. Supreme Court, in Congress, and in the Trump Administration are denied communion, or even excommunicated? What happens if Pope Leo declares that Trump and his minions are servants of Satan?
The Papacy hasn't tried anything like that for centuries. But there are precedents for a Pope doing so. If Pope Leo sees Trump acting increasingly like Hitler towards a population that is mostly Catholic, the Pope has plenty of room to escalate and the institutional capacity to coordinate that effort in a way that few other movements in the U.S. can.
Even if the Pope and his bishops and clergy do nothing more than throw shade at Trump, that's something that could flip a lot of swing voters (and not just Catholic ones).
* Southern voters burned by hurricanes, floods, tornados and other natural disasters and denied the federal disaster relief assistance that they've become accustomed to are another set of enemies who will burn hot to oppose Trump and weren't expected what they got, even if Trump campaigned on it. It isn't even just a matter of the economic substance of it. A big part of Trump's appeal in Red States was the perception that he cared more about people like them than the Democrats did. His indifference to their suffering during disasters undermines that perception.
* Veterans tend to vote conservative, but have received almost no respect, with Trump repeatedly disparaging them, and have seen programs for their benefit cut mercilessly. Some veterans will see this as breaking faith with them and dump him. Veterans disproportionately subscribe to a culture of honor, something utterly foreign to Trump.
* Farmers and small business owners, especially in rural America and small towns, who have been badly hurt by Trump's trade policies, the deportation of their workforces, the imminent shutdown of their local hospitals, and deep cuts to their community schools are another set of potential enemies.
* Everyone involved in the healthcare industry has been alienated by Medicaid cuts, immense threatened pharmaceutical tariffs, indiscriminate cuts to medical research that weren't telegraphed on the campaign trail, and the utter insanity of RFK, Jr.'s pseudo-scientific approach to public health, even wealthy doctors who benefit from his tax cuts.
* The tax cuts Trump has provided to Wall Street and big business are meaningless if they are losing money, which his disastrous trade policy, threats to the independence of the Fed, and the damages he has done to the value of the dollar and the credit rating of the United States has done.
* Trump has flipped Elon Musk from being "co-President" to his enemy. The richest man in the world is a formidable foe, and is the leader of the coalition of tech billionaires that backed Trump. Musk's proposed "American Party" could also split the conservative vote and hand victory to Democrats in many races.
* Non-MAGA smart conservatives from federal judges, to think tank figures and professors, to older generation Republican leaders, to pundits, to military officers, are not keen on some of the directions Trump is taking, such as disregard for rule of law, civility and respect, and his anti-intellectualism, even if they like many of the changes he has made in substance.
* Federal employees are the source of every federal elected official's power. And, Trump has done everything he can to purge civil servants who won't be loyal to him and to cow those who are left with fear. But he's shed a lot of competent seasoned officials, made life very hard for those who are left, and betrayed the longstanding trust of almost every federal employee. So undermined, the federal government is going to be a lot less competent and effective, and federal employees will be looking for passive-aggressive ways to undermine him at every turn. no matter how hard he tries to assert control. And, a large percentage of federal employees who have abruptly seen their secure, high prestige futures shattered are now on a singular mission to use their insider knowledge and connections to fight him with all of their being.
* Educators from every school and higher educational institution in the country now see Trump and the GOP as their unequivocal enemies. While this was never an industry that strongly backed the GOP before, their long standing efforts to be neutral towards the GOP have been shattered now that the GOP has declared outright war on all of them. These institutions are strong not only in their own right, but also because they have a carefully cultivated and nurtured alumni base who will be willing to go to bat for them that includes many powerful, rich, and influential people.