Obama would NOT need 67 votes out of 100. He just needs 2/3 of those physically present at a particular moment in time.
Suppose the Senate is in session, and there are but a handful of left-wing Senators present since the Senators are all scattered at their offices or in committee hearings.
The way this is written, any treaty could be passed at any time with say 34 out 51 (a usual quorum). What about 7 out of only 10 present if they carefully time it? What about 3 out of only 3 present when the left-wingers keep a running count? How many minutes does it take to ram through a vote with no regard for "Senatorial courtesy"?
Would you want to be one of those 3? Seriously, I think that even Upchuck Schumer isn't that stupid - because he simply cannot be guarded out to a range of 500 yards on a 24/7/365 basis, no matter how many security people he has working for him. FYI, I'm not threatening anyone, nor am I encouraging anyone to engage in any illegal act(s) - I am merely stating what I believe to be the facts.