First, your premise is wrong. It has been the stated policy of the United States, whether GOP or Dem not to negotiate with terrorist. Dealing with Terror supporting state actors is another thing altogether. Neither presidents of either party have an unblemished record on this account. Reagan sent weapons to Iran and supported Iraq when it was convenient. Bush supported Noriega, who was funding narco-terrorist, and then turned on him. It goes on. As to Iran circa 1978, short of a directly military involvement, it was unlikely that the Revolution would not have occurred, considering the US had supported the Shah for some 20+ years, both Dem and GOP presidents, so the US had virtually zero cred with the Iran people.