Obligation? Who cares what the broad the President is sleeping with does? I am very excited by this just for the fact that these First Ladies seem to get their fingers involved in things that they have no business in. Hitlary and Hitlarycare and the Moochelle School Lunches come to mind. I vote for a President, not the broad they're banging. I also like that Donny will be focusing on work and not getting yelled at for leaving the toilet seat up.
Yes obligation. It's not just some broad he's sleeping with, Melania happens to be his wife and mother to his son. First Lady's have always took on at least some type of 'stewardship' role in their husband's presidency's Most influential that come to my mind are Nancy Reagan, Barbara and Laura Bush, Eleanor Roosevelt, Betty Ford, Jackie O., etc.
Melania though doesn't look comfortable being his wife, let alone being the First Lady of the United States and she was pretty much absent from the campaign trail. I find it very unusual actually. Perrhaps this is why rumors have been floating around that Trump's daughter Ivanka will fulfill the role?