Even if President Obama is (against all odds and logic) right about how spectacular the proto-deal with Iran is, if Iran wants nukes they will find other ways to get them.
Like from North Korea:
American defense officials believe that North Korea has mastered the technology to build a nuclear weapon that will work on a ballistic missile.
Don't be silly, you say! North Korea and Iran working together?
Wait. What? North Korea's missiles benefited from Iranian help?
Ally Iran has made considerable progress in developing large solid fuel rocket motors and that technology would be available to North Korea. Iran got this tech from Pakistan, who got it from China who got it from Russia which stole it from the United States.
And don't forget that when Israel bombed that Syrian reactor, before anyone was sure what was going on the North Koreans blasted Israel for killing North Korean technicians at the site.
Syria even then was a client state of Iran.
Where else might Iran get the tools for nuclear weapons outside of the parameters of our carefully crafted deal, eh?