Richard Nixon negotiated “Peace With Honor” and the Dems in Congress then cut off the military assistance is the story I experienced as a child.
I also supported Dr. Carl McIntire who marched for World War II style victory in Vietnam and lost his radio station to the Fairness Doctrine of the FCC for it.
The liberals complained about him to the feds and the Republican run FCC pulled the license.
That was the double tap...
The Democrats had throttled the equipment & ammo replenishments for the South almost 18 months before the final act you mentioned...
Their reasoning was that it was important to snatch defeat from the jaws of victory...
Precisely what they (now, the American Communist Party) has done in virtually every war since...