Jeb, Scott, Marco, Rand, Chris, Mike, Ted and Rick. The contest among these powerful Republicans for the presidential nomination promises to be a free-for-all. We cannot predict which candidates will shine in the debates, and which will stumble over their shoelaces.

One thing is sure — the Republican presidential nominee will once again have a set of XY chromosomes, while the Democrats seem poised to make the first major party nomination of a woman at the top of the ticket (provided Hillary Clinton doesn’t find some new and ingenious way to disqualify herself). With the prospect of a woman at the top of the Democratic ticket, and a long trail of elections lost to the “gender gap,” the Republican who emerges from the testosterone-rich presidential pack will almost certainly choose a woman as a running mate.

That woman will need to be appealing to voters, conversant with the issues and tough enough for a national campaign. There are several Republican women who might fit this bill, from New Mexico Gov. Susana Martinez to South Carolina Gov. Nikki Haley. Smart money, though, would have to go to Sen. Kelly Ayotte of New Hampshire.

A former prosecutor, Ayotte served as the chief of the New Hampshire Homicide Unit and deputy attorney general before being appointed state attorney general by a Republican governor — and then twice reappointed by a Democratic governor. A tough prosecutor, she secured New Hampshire’s first capital murder conviction in 60 years. Ayotte now brings her tough-mindedness to the life-and-death issues of the Senate Armed Services Committee.

How would she do as a national candidate? I had a chance to see Ayotte face a minor test when she had to react in real time to a breaking national event. Ayotte spoke Thursday on the campus of the University of Texas at Austin shortly after President Barack Obama issued broad details of his framework nuclear agreement with Iran.

Like a lawyer presenting a brief, Ayotte skillfully dissected the assertions of the administration, and compared its hopes against the sober realities of Iranian behavior. Ayotte began by speaking about the failure of the international community to dissuade North Korea from developing a nuclear weapon, a regime that promised to comply with the nuclear non-proliferation treaty, only to withdraw from all agreements and develop nuclear weapons when pressed on verification. “That is history we do not want to repeat,” Ayotte said.

She then noted Iran’s unrelenting hostility to the United States, beginning with the taking of U.S. diplomats as hostages in 1979, to the leading of a “Death to America” chant last month by Iran’s Ayatollah Ali Khamenei. Ayotte laid out Iran’s spreading influence through terrorism, from producing the roadside bombs that “murdered and maimed many of our soldiers,” to the recent takeover of Yemen by Iran’s Shiite proxies.

“Iran is not an easy partner to work with,” she said with deadpan understatement. She noted Iran says it has developed a new generation of centrifuges that are 15 times faster in enriching uranium, while Iran’s navy recently conducted a simulated attack against a mock U.S. aircraft carrier in the vicinity of the Strait of Hormuz. To make matters worse, Ayotte said that the public estimate of when Iran would be able to field an intercontinental ballistic missile capable of hitting the United States is this year.

With so little basis for trust, Ayotte concluded that in order for any deal to work, it must allow international nuclear inspectors to go anywhere in Iran they want without notice and without delay. “Anything short of that, it will be very difficult to make sure that Iran is complying with this agreement,” she said.

Ayotte spoke with some passion about the role of the U.S. Senate in “one of the most important arms control agreements since the end of the Cold War.” She was an early cosponsor of a measure with strong bipartisan support for allowing Congress to review any agreements with Iran, including the ability to impose new sanctions on Iran within a 60-day period.

“It was the Congress on a bipartisan basis that actually put the toughest sanctions in place,” Ayotte said. “Before they are removed, we have a constitutional role in ensuring that the agreement is one that we think really protects the interest of the United States of America … I respect the president’s Constitutional role. But I hope we will be given a broader opportunity to review this agreement. And it can’t be that the administration would go to the U.N. but won’t come to the United States Congress.”

In Austin, I saw Ayotte react to a complex event with high stakes in a critical, but thoughtful way. She spoke like a senator, and maybe soon, something more.