Sen. Tom Cotton, R-Ark., on Capitol Hill. (Tom Williams/AP)

Sen. Tom Cotton was working to build support for his now-controversial letter to Iranian leaders when he ran into an unexpected obstacle: Mother Nature.

“As a practical matter, the snowstorm really impeded my efforts,” said Cotton (R-Ark.), in reference to the late-winter blast that led lawmakers to rush home from Washington last week. “Everybody left on Wednesday, so I had to mostly work the phones into the weekend.”

But by the following Monday, Cotton had gotten got 46 of his 53 Republican colleagues to sign his letter, crafted to sink a potential international deal on Iran’s nuclear program. But he also drew sharp rebukes from President Obama and many other Democrats who condemned the letter as a partisan stunt and a dangerous act of defiance.

Cotton, 37, a lanky, Harvard-
educated Army veteran of the wars in Iraq and Afghanistan, said he wasn’t surprised by the backlash.

“They know they can’t defend the terms of the deals they are negotiating,” Cotton said in an interview Tuesday. In less than three months, Cotton has emerged as one of the most aggressive national security hawks in the Senate, audaciously challenging Obama’s foreign policy with harsh rhetoric and confrontational tactics.

An already heated battle between the White House and Republicans over negotiations to curtail Iran’s nuclear program grew more tense when 47 Republican senators sent a letter to Iran designed to kill any potential deal. But is it treason? (Jason Aldag/The Washington Post)

Unlike the 2010 Republican wave election, which produced a class that flashed a non-interventionist, war-weary streak embodied by Sen. Rand Paul (R-Ky.), the 2014 class is a more hawkish crowd.

All 12 Republican freshmen signed Cotton’s letter. A quarter of them have served in the military: Cotton and Sens. Joni Ernst (Iowa) and Dan Sullivan (Alaska).

“I do think it reflects well that the freshman class all joined it, because we ran in an election in which national security was an emerging theme,” Cotton said.

Cotton said he first drafted his letter two weekends ago. He unveiled it at a Senate GOP lunch last week and lobbied hard for signatures in the ensuing days, contacting every Republican senator and reaching out to some Democrats.

No Democrats signed on and many were exasperated by its existence.

Speaking at a Senate Foreign Relations Committee hearing Wednesday, Sen. Chris Murphy (D-Conn.) called the letter “unprecedented” and said it was “undermining the authority of the president.” Murphy asked Secretary of State John F. Kerry for his reaction.

“Utter disbelief,” responded Kerry, who was testifying at the hearing on Obama’s request to authorize the use of force against the Islamic State.

Seven Republicans declined to support Cotton’s letter, including Foreign Relations Committee Chairman Bob Corker (R-Tenn.). Corker said he was hopeful that Republicans and Democrats could overcome the rancor that has roiled the debate over Iran policy.

“There have been a lot of tensions,” said Corker, adding, “Hopefully, we’ll move beyond that and be in a place where we can soberly and responsibly address” any deal that is reached.

Sen. Susan Collins (R-Maine), who also declined to sign the letter, said Cotton’s strategy didn’t seem fitting.

“I felt that our advice ought to be directed to the president of the United States, to the secretary of state and to our negotiators,” Collins said. “It did not seem to me to be appropriate for us to be writing the ayatollah at this critical time during the negotiations.”

Cotton also has faced criticism from outside the government. The Wall Street Journal editorial board called Cotton’s letter a “distraction” that enabled Obama to complain that Republicans were simply lobbing partisan barbs.

“The security stakes couldn’t be higher if Mr. Obama enables a new age of nuclear proliferation, and Republicans need to keep focused on a critique of the deal’s substance,” the board wrote. “Giving Mr. Obama a meaningless letter to shoot at detracts from that debate.”

Cotton has drawn widespread attention this week, but it’s not the first time he has landed on the national radar. He also attracted attention at a February Armed Services Committee hearing when he said that Guantanamo Bay detainees can “rot in hell.”

Cotton’s views on national security appear to have been shaped in large part by his military service.

“I certainly haven’t forgotten that Iran killed hundreds of troops in Iraq,” he said.

The Obama administration is in talks with Iran about limiting its nuclear program and ensuring it cannot create a weapon, in exchange for the potential easing of economic sanctions. Cotton, who called for ramping up sanctions in 2013, warned that those negotiations could lead to a perilous place and that the Iranians are not to be trusted.

“He may be about to announce a deal that is unwise and very dangerous,” Cotton said of Obama.

In the 2014 campaign, Cotton was seen by Republican officials as the rare recruit that excited the tea party and the GOP establishment. Democrats criticized him for being overly ambitious as he geared up for a Senate campaign soon after being sworn into the House in 2013.

Pressed on how he envisions his first two years in the Senate, Cotton mentioned stopping Iran from obtaining a nuclear weapon, curtailing the threat of global terrorist networks and “rebuilding” the military.

“National security is always the foremost responsibility of the federal government,” he said.

Cotton is having no trouble keeping busy or staying in touch with leading party strategists. Waiting outside for a personal visit with the senator after his interview was Lanhee Chen, Mitt Romney’s 2012 policy director and a Harvard classmate.

There even is a movement in Arkansas to clear the way for Cotton to simultaneously run for reelection to the Senate and for president in 2020.

“Tom Cotton would be my current idea of someone who should be afforded this opportunity,” state Sen. Bart Hester (R), who is pushing a bill to allow a candidate to appear on both ballots, told the Associated Press.

At one point in the interview, an aide interrupted to tell Cotton that he had a “very important call” he needed to take from one of his colleagues.

When the interview resumed, Cotton and a reporter tried to recall where the discussion had left off and what he was saying.

“I don’t know, but it was brilliant, wasn’t it?” he quipped.

Mike DeBonis contributed to this report.