[Gorwingel]

Why don't we just look at it from the viewpoint of Aragorn defeating the Dark Lord. I think that hopefully the people of Gondor would have seen that Aragorn was most definitely a more effective leader just because he had ridded them of their greatest foe, and Denethor had not. So, yes, I believe if Denethor would have still been alive he would have stepped down just because of overwhealming public opinion (Now I know that Gondor was most definitely not a democratic society, but hopefully Faramir would have gotten on the side of Aragorn, and hopefully public opinion would have swayed on to the side of Aragorn). But then I also believe that he wouldn't have stepped down non-violently. He was very much a strongwilled character, and would have most likely ended up either being killed sent into exile in some way.