One of the arguments for the Iran nuclear deal was that it would encourage greater openness and investment from the West. But Iranian hard-liners have been working in recent months to sabotage the proponents of economic globalization and change.

Can an American president make big, historic changes in the country’s direction with a relatively narrow base of political support? That was the challenge President Obama faced when he pushed health-care reform through Congress, and it’s the same problem he faces now in trying to win support for a breakthrough nuclear deal with Iran.

Obama was confident and combative as he made his case this week on Iran. He delivered a powerful speech enumerating the virtues of the agreement. But he included some partisan lines that riled opponents (and some fence-sitters, too), and it’s questionable whether the speech, masterful as it was in analysis, will add any votes of support.

As the Obama administration moves into a decisive stage of nuclear negotiations with Iran, officials are considering a two-step process that would begin with a freeze and modest rollback of Iranian enrichment of uranium, matched by a limited easing of U.S.-led economic sanctions on Tehran.

In the late 1950s, the famous nuclear strategist Herman Kahn facetiously suggested building what he called a “Doomsday Machine.” A computer would be wired to detonate a vast array of nuclear bombs if the Soviet Union took an action defined as intolerable.

The U.S.-Iranian diplomatic train is rolling fast, with President Hassan Rouhani talking Wednesday about a three-month timetable for a nuclear deal. But Rouhani was also cautiously insistent about staying on the single track of the nuclear issue — perhaps fearing that if this becomes a runaway, it will derail.

How did it happen that, less than a year after Barack Obama convincingly won reelection, his every move as president now draws hoots and catcalls from every point on the political spectrum?