The so called phased or step by step approach with reciprocal concessions. Therefore it would be difficult to characterize it as a sweeping success, even if there are positive concessions from North Korea. Early on Bolton castigated this approach and preferred the unrealistic "one bundle" or "Libyan approach," to negotiations which demonstrates his incompetence in Asian affairs if not in diplomacy generally.
The negotiations will begin to look like what occurred before in the six party talks, and agreed framework. This has been the inevitable trend all along, although the administration denied it at the outset because it contradicted their campaign promises. The negotiating approach will look more and more like the previous democratic approach to North Korean denuclearization in the past.
Whether the second summit is a "success" or not, will be more about the spin put on it by the media than anything else. Negotiations are a process, they can fail in a moment, but they can only "succeed" over a protracted period of hard work by people who know what they are doing. Any concessions by the US in return for concrete steps to disable nuclear production facilities and open them to inspection will predictably result in a media and MIC think tank uproar.
Fortunately, Biegun appears to be at this point, more competent, than any other person the administration has. We can tell this from the criticism from the Washington Post's Josh Rogin:
The State Department has been working on better coordination with Seoul, establishing a working group under special envoy Stephen Biegun, the lead U.S. negotiator. But recent reports suggest the United States is moving closer to Moons position, not the other way around.
The negotiations should be left to Biegun and his working group. But inevitably whatever happens at the summit will become a domestic political football disconnected from the real issues.
https://civilizationdiscontents.blogspot.com/2019/02/interim-us-negotiating-strategy.html