Would Vietnam have more defenders? Would more people support the draft?
Without the Watergate scandal the US Congress might not have cut off support for the Republic of Vietnam at a time when the NVA was building up hugely in size and firepower.
The US continuing to provide and pay the technicians who kept the helicopters etc flying would be a huge help since South Vietnam, as a third would country with a GDP per person of $100 per annum could not support or pay for the military it had - 1 million man army, world 5th largest airforce - by itself.
That the NVA was transitioning from having 100,000 men in-country at any given time to double that and more, from a 'no weapons that can not be carried on a mans back' policy to having a large tank force defended by an integrated SAM and AAA system at the same time that the South was having its mobility and air support cut off by funding and support staff cuts; this doomed South Vietnam.
If Nixon had still been president he might have been able to prevent this, or at least make clear that it was happening and bound to lead to disaster. That would change the political calculus.