She was calm, articulate and relentless – and unlike the two candidates, moderator Martha Raddatz of ABC News was the undoubted star of this year's vice-presidential debate.

Raddatz never lost control, not of time nor of substance, unlike her predecessor, Jim Lehrer, in last week's presidential campaign debate. She hit all the tough questions expected of a candidate for US vice-president, with a detailed, precise knowledge. She was low-key but gracefully on point enough to steal the show.

To Congressman Ryan she said gently on Libya: "I just want to talk to you about right in the middle of the crisis. Governor Romney, and you're talking about this again tonight, talked about the weakness, talked about apologies from the Obama administration. Was that really appropriate right in the middle of the crisis?" The rebuke was implied, but all the more effective for being so. It put Ryan on the defensive and Raddatz shone as the woman who had shown him up. She didn't go much easier on Biden either. Biden was like the boy debater who'd had a Red Bull with a Gatorade chaser backstage. He wanted to argue with anyone in sight at the top of his voice till the clock ran out. But Raddatz quietly reined him in. (crosstalk) Biden: "With all due respect, that's a bunch of malarkey."

Raddatz: (without a beat) "And why is that so?"

Biden: "Because not a single thing he said is accurate."

Raddatz: "Be specific."



She controlled the candidates to the extent that she got them to face (albeit unwillingly at times) the tough topics she had come up with.



"Should the US have apologised for Americans burning Qur'ans in Afghanistan?" she asked Ryan. "Should the US apologise for US Marines urinating on Taliban corpses?"

The directness of her approach sped up the debate process even as it occasionally left the candidates struggling for words. But when that happened, she was a helpful prompter.

Ryan: "Oh gosh, yes, Urinating on Taliban corpses? What we should not apologise for …

Raddatz: "Burning Qur'ans immediately?"

Ryan: "What – what we should not be apologising for is standing up for our values ..."



Domestically Raddatz took them to task on health, then senior care. And then she came at them with this:



Raddatz: "If your ticket is elected, who will pay more in taxes. Who will pay less?"

As Ryan waffled on detail, she interrupted him.

Raddatz: "Do you have the specifics? Do you have the ..."

Biden (interrupting): "That would be a first for the Republican Congress."

Raddatz: "Do you know exactly what you're doing?"



Specifics, precision, exact answers. This is not a concept that American debates with their waffly pre-planned written essays for answers are used to. By the time Raddatz got to talk to what half the voting population saw as the highlight of the debate, there was real excitement around America's television sets and computer screens, despite a lengthy detour on defence spending and the US presence in Afghanistan.



Raddatz: "We have two Catholic candidates first time on a stage such as this. And I would like you both to tell me what role your religion has played in your own personal views on abortion … please talk personally about this if you could."



(I'll distill the answers here in the interest of space)



Ryan: "Why am I pro-life? It's not simply because of my Catholic faith … It's also because of reason and science … The policy of the Romney administration will be to oppose abortions with the exceptions for rape, incest and life of the mother …"

Biden: "My religion defines who I am … But I refuse to impose it in equally devout Christians, Muslims and Jews. I do not believe we have a right to tell … women they can't control their body."



The thoughtfulness of her questions forced the candidates to reveal more of themselves than perhaps they wanted to. For example, the low-key question at the end: "If you are elected what can you give to this country as a man as a human being that no one could?" could have been answered any one of a hundred ways.



Which meant that many of the answers could be filled with potholes. How do you define yourself? Do you even try? If you don't, are you missing an opportunity?



It did look like something of a copout when instead of responding to Raddatz's opportunity to reintroduce himself, Ryan ducked and returned to spouting economic solutions. The better turn was performed by Biden: "Look at my record," he began before defining himself as someone whose whole life had been about working for improvements for the middle class.



At the end of the debate, liberals praised Raddatz for doing a thorough professional job. Conservatives continued to lambast her bias for the fact that Obama had attended her wedding while at Harvard Law School 21 years ago. (She is since divorced.)

But of the three personalities on stage there was one clear winner, and it was not a man, nor a candidate. Congratulations, Martha Raddatz.