For example, when you visit the campus, do they make you sign into some online portal or something? Also, I’m aware that applying ED is the main way to track demonstrated interest.
Someone just got admitted without visiting the campus before. Considering the admit rate for RD is only 6% or so, I highly doubt anyone would have been admitted without a campus visit if it were considered. It’s really not. Your interest is already demonstrated by your application. The only bonus they give you is if NU is your first choice which is demonstrated through ED.
Northwestern’s common data set says they do consider demonstrated interest.
I believe when we visited advanced registration was required and we signed in.
Ok thanks!
@VaibhavKeshari Just let you know that my DD got admitted to NU without visiting the campus.
@Junerain I’m sure it’s possible but why not visit the campus if it’s close to you AND helps your app. I’m gonna go anyways bc. its one of my top schools so I wanna get a feel of things there, but was just wondering whether it’ll give me a small boost. Thanks for your input though 
@VaibhavKeshari In the early stage of the last application cycle, NU was not within our radar. Therefore we did not visit it. Then later we found NU was a great fit to D’s interest and decided to apply it anyway. Luckily D was admitted and very happy about it.
By saying so, I agree that you’d better visiting if you have time and money to do so. We actually had visited 8 schools during the last application cycle. Ironically, however, the top 2 schools currently we have not yet decided which to pick (Northwestern and Dartmouth) are the only two schools D applied but we did NOT visit.
Visit if you can, but I strongly suggest that you do the interview. When I interviewed, my interviewer told me tat one of the categories for evaluation is interest. If you assert your interest during the interview, it will reflect well upon you.