It really comes down to the second/third round. The first round will include a large number of votes for odd locations so that individuals know their vote was included. If North South Funkadelick Texas isn't listed, a ballot wasn't counted. In the second round, all of those will be redistributed. The four official bid totals will be counted. If any one is 50.1 percent they are the winner. The lowest vote getter drops and redistributes. Now if the combined total of Japanese/Canadian votes (assuming they all put the other as #2) puts the Canadian/Japanese bid in 2nd place, then either Helsinki or DC would be dropped and their votes redistributed... I have no idea where the DC/Helsinki votes would go... Based on the number of votes I've heard Helsinki is carrying in and the push DC is planning onsite, I believe it is unlikely. But it is likely that Canadian and Japanese voters will determine the site of the 2017 Worldcon.
That truly is the wild card. There are two distinct groups of puppies. Vox Day/Theordore Beale has supported a bid, or so I hear. (thankfully not DC17). So how the two groups vote or don't vote is big. Then there are the large number of reaction voters that came in after the nominations. If they vote in site selection... who knows.