Last week during the most-watched primary debate in history, a U.S. senator fired a cogently argued objection at his party’s leader, drawing a contemptuous and insulting personal attack.

No, it wasn’t Sen. Rand Paul who chastised Donald Trump for being “on every side of every issue,” criticism for which Trump poked Paul for “having a bad night.”

It was Sen. Chuck Schumer who, after taking a month to Think Again about the Iranian nuclear agreement, announced his carefully considered rationale for opposing President Obama’s controversial foreign policy objective – an accord that reverses America’s long-standing policy to prevent an Iranian nuclear weapon and the proliferation it would spawn.

Schumer judged the deal not on “whether the agreement is ideal, but whether we are better with or without it.”  He concluded we’d be worse off and less able to thwart the world’s foremost sponsor of terrorism after giving Iran’s “brutal, theocratic” regime $50-150 billion in unfrozen assets to “pursue nefarious goals,” and allowing them to become a nuclear-threshold state.

Schumer’s conclusion reflects the opinion of experts who’ve appeared before Congress, including Amb. Robert Joseph, chief U.S. negotiator of the 2003 Libya deal that dismantled the country’s nuclear program.

Calling the Iran deal a “bad agreement” with “fatal flaws,” Joseph testified “the threat to the U.S. homeland and to our NATO allies of an Iran armed with nuclear-tipped ballistic missiles will increase, not decrease, under the anticipated agreement.”

Schumer cited the ayatollahs’ long track record of deceit and deception, and their "tight and undiminished grip on Iran," in deciding it’s “better to keep U.S. sanctions in place, strengthen them, enforce secondary sanctions on other nations, and pursue the hard-trodden path of diplomacy once more, difficult as it may be.”

Unwilling to tolerate principled opposition, deal supporters launched a vicious smear campaign, branding Schumer “Warmonger Chuck,” even though Americans by a two-to-one margin oppose the Iran deal and believe it will make the world less safe, according to a recent Quinnipiac poll.

About the presumptive next Senate Minority Leader, White House Spokesman Josh Earnest suggested Democrats should “consider the voting record of those who want to lead the caucus,” proving Voltaire’s observation: “it’s dangerous to be right in matters where established men are wrong.”

Schumer’s lambasting followed Obama’s speech at American University, the stage from which President Kennedy made his case for the 1963 Nuclear Test Ban Treaty. “Let us not be blind to our differences,” Kennedy encouraged, “but let us also direct attention to our common interests and to the means by which those differences can be resolved.” The Senate voted 80-19 to ratify the treaty.

Standing in Kennedy’s place, Obama dismissed critics who are concerned the Iran accord doesn’t reflect pre-negotiation promises, saying it’s not a “tough call” to support the deal. After insisting the only alternative is “another war in the Middle East,” Obama denounced opponents’ “knee-jerk partisanship,” “stridency” and “lobbyists” demanding war.

“It's those hardliners chanting ‘Death to America’ who have been most opposed to the deal. They're making common cause with the Republican Caucus,” Obama charged, as if America’s duly-elected representatives are the moral equivalents of unelected theocrats who stone women, hang gays, and shoot peaceful protestors.

Supreme Leader Ali Khameni has already violated the deal, most significantly by having his top aid declare, “entry into our military sites is absolutely forbidden.” Yet Obama maintained the deal “permanently prohibits Iran from obtaining a nuclear weapon,” one of many evidence-free assertions that underscore Kennedy’s key insight: "no treaty ... can provide absolute security against the risks of deception and evasion."

Equally practiced in the art of evidence-free political rhetoric, Trump is a word salad-spewing colossus atop an untidy Republican presidential field. The ultimate anti-politician to disaffected voters enraged by ruling elites and political correctness, Trump wins plaudits for disparaging “stupid people” and those who “don’t treat me nice” – not for persuasive abilities.

All style and no substance, even on issues that make supporters swoon – illegal immigration, trade deals, Planned Parenthood – Trump is imprecise, incoherent, and inconsistent, though it matters not to his champions. Asked about Iran in last week’s debate, Trump mustered “I would be so different from what you have right now. Like, the polar opposite.”

Our democratic system relies on leaders who say what they mean and then get elected to go do what they said. More than celebrity, Trump’s surge derives from a smoldering frustration with politicians who don’t respect their contract with the people.

On the high-stakes Iran deal, Obama is poised to override the will of the people, and an overwhelming bi-partisan majority in Congress, unless Americans insist otherwise. Kennedy was right, “Let us not seek the Republican answer or the Democratic answer, but the right answer.”

Think Again – May the right answer on the Iran deal emerge from an open, informed and respectful debate in Congress next month.