Moderator Raddatz kept the trains moving

• Raddatz was more involved in the debate than Jim Lehrer
• She asked direct questions, and stayed on the candidates when they didn't answer
• Raddatz would bend the debate rules for each side, but not allow them to be broken

You pick a tough moderator, you get a tough debate.

And odds are, you won't find one much tougher — or who performed much better — than ABC's Martha Raddatz, who moderated Thursday's vice presidential debate between Vice President Joe Biden and Congressman Paul Ryan. She doesn't deserve all the credit for a livelier debate than the first presidential session; the candidates had something to do with that. But she certainly helped move it along. And she did it without doing a disappearing act.

What we've seen in the two debates is two diametrically opposed approaches to the moderator job. In the first presidential debate, Jim Lehrer approached the job as a conversation facilitator, asking open questions and then letting the candidates speak as long as they wanted about whatever they chose. Raddatz clearly saw her role differently, asking more direct questions and challenging the candidates when they didn't answer.

She proved it from the start. Raddatz asked Biden about the murder of our ambassador in Libya and Ryan about whether it was proper for Romney to hold a press conference on the subject, two topics neither candidate could have welcomed. When Ryan tried to talk about something other than Iran, she told him to talk about Iran. When Biden tried to interrupt Ryan's answer on unemployment, she made him wait his turn.

It helped, perhaps, that she was sitting at a table with them rather than sitting downstage while the candidates were upstage at podiums, the situation Lehrer faced. As every parent knows, it's harder for children to misbehave when they're within your reach.

That doesn't mean that she was some debate-moderator martinet. She allowed the rules to bend, she just didn't allow them to break. When Ryan went overtime on his tax answer, she didn't interrupt, but she didn't allow it to happen without promising Biden he could go over as well. She challenged Ryan on his tax numbers and Biden on Afghanistan, but did both without coming across as unfair or improperly aggressive. And she led them into a personal discussion of abortion, which provoked some of the night's best answers.

By knowing when to be assertive and when to lay back, Raddatz was able to control the debate without unduly limiting the give and take between the two participants. And the result was a more focused conversation with less wandering from the candidates — in large part because when one of the candidates avoided a question, she asked it again. She kept the trains running, which is part of a moderator's job, but she also did her best to keep them on the proper track.

The most important people Thursday night, of course, were the debaters, not the person leading the debate. As Gwen Ifill said on Twitter, when she asked people to stop attacking the moderators, "they're not on the ballot."

Still, they are on TV. And the last time any of us looked, that was enough to open someone up to criticism. People who don't like it should choose a more private profession.

Or do this one as well as Raddatz.