It doesn't matter whether the president has a D or an R after his name. What matters is that we are able to verify that the Iranians have actually quit trying to make a bomb, and, if they haven't, that we reestablish the sanctions.
and, if the sanctions don't work, and Iran gets a nuke, then the (bleep!) will really hit the fan. Then the choices are between invading Iran, watching while Israel attacks Iran, Wringing our hands and hoping Iran doesn't actually use the nuke, or blaming the party of the of the president when and if they do get a nuke.
Unless there are some major changes in Congress, the latter option will be the choice made.