This is far scarier than any single rule about research grants, and I'm not sure why nobody's talking about this.
The OMB writes the budget to enact federal policy. And critically, no federal regulation can exist with the OMB approving it. By making this appointment explicitly political, they have carte blanche to completely rewrite all federal regulations to be exclusively conservative ones. This would have been crazy to attempt before, but with Trump 2.0, this is the new norm.
One of the things they are doing right now (it's been approved and the rules are now active and legal, so it is now happening) is converting 50,000 civil servant jobs into political appointments. This means having a job in government no longer serves the whole nation, it's now an ideological function to serve a single political party. Literally weaponizes the federal government to punish opposing political views and enforce one view on everyone (there's no other point to political appointment). And if the party in charge ever changes, it now means everyone will be laid off and replaced. Every few years. So nothing will ever get done in government now, except for extreme short-term pushes for radical political agendas, because nobody will stay long enough to know how the government works to do anything else. Move fast and break things with the largest economy in the world, radical political agendas, and 380M people.
The OMB also can review and block all proposed legislation going to Congress, vet all official congressional testimony, and block any agency from publicly disagreeing with the President. Military generals, health officials, science experts, ecologists, intelligence directors... they can block all of them from giving any testimony to Congress. That's an actual power the OMB has.
They can also block money Congress has already allocated, meaning that your representatives in government are now completely useless, because whatever party is in the Executive can nerf anything your reps have passed. The Supreme Court could do something about it, but won't, because it's now a Conservative Supermajority. There is no reason for them to disagree because they already ideologically agree.
Finally, the OMB can issue a rule that every agency that wasn't officially under the Executive before, has to submit all its rules for Executive approval. Meaning the Executive would control all government agencies.
In any other context, in any other country, this would be called a single-party authoritarian coup. When they create rules that outlaw other political parties (that's what authoritarian governments do to retain single party control) - and assuming the democrats don't just give up - it will be the official start of civil war. Coming to you Fall 2028.