The smartest thing he arguably could do, would be to just walk away.
Explain that this was all Biden’s fuckup, Ukraine and Russia aren’t willing to settle so he’ll withdraw all aid and review sanctions to see which one cost America money. And of course add that if the two are willing to settle in the future, America is ready to be a broker.
Unfortunately Trump and the Ukraine war is a prime example of "damned if you do, damned if you don't". There is no walking away for him, at least without suffering an extreme political blow, though the other options aren't any better for him. Out of all of the possibilities the only one that won't end with every media outlet, neocon, neolib, glowie subversive, antifa thug, and GAE supporter won't milk for all its worth to destroy him and his movement (or at the very least cause as much internal chaos for the administration as possible) is the one that will never happen.
If Trump walks away after Ukraine proves to be a Shortfatotaku tier bad faith actor in negotiations then its collapse will be pinned solely on him and everything pre January 2025 will be rapidly forgotten to paint the picture that victory was just around the corner before it was sabotaged by le orange Russian agent.
If Trump doubles down on supporting Ukraine if it collapses without dragging NATO into a war then he will still be blamed, most likely under the narrative that he was some Hitler like micromanager who messed up the resources at his disposal to win a war that Biden would have won on January 21st.
If Trump goes to war to save the Kiev Junta then every troon who in March 2022 screamed for a no fly zone, every dem congressman who wanted to spend trillions to fund Ukraine and every NAFO glowie who demanded war will unite in oppossition instantly to getting what they wanted, not because they miraculously will start to want peace the moment U.S troops start (officially) dying or will be taken aback by the reality that there is nothing at any given moment to prevent them from being minutes away from incineration but rather because they will simply parasitcally hop onto the anti war sentiment that will sweep the nation, rewrite recent history to make themselves out to be the anti war voices of reason, and try to regain full control over America before promptly continuing the war.
And lastly if somehow Trump masters the art of savescumming until he leads Ukraine to victory without Russia unleashing its entire nuclear stockpile then all his opponents will downplay it into a nothingburger and insist that AKSHULY Biden had already won the war and that he had as much to do with the victory over Putin as Truman did over Hirohito.
It doesn't matter if you hate him or think he is the best mortal to ever live, you at least have to concede that he has been put into a impossible position, one where its only a matter of limiting the fallout once the inevitable occurs and half of the country will make the reaction to the Fall of Saigon look tame.