NEW YORK (AP) — The debate season that has chewed up its moderators comes to a close on Wednesday when John McCain and Barack Obama meet for the third time, with CBS News' Bob Schieffer directing the discussion.

The veteran "Face the Nation" host won't telegraph what he will ask. But he said he will be seeking more details about their potential presidencies than have been evident so far.

"By now we've all heard their talking points," he said. "We've heard the general outlines of what they are talking about. The time has come to be a little more specific."

Jim Lehrer, Gwen Ifill and Tom Brokaw had great plans going into their debates, too. Each had their own frustrations.

Lehrer tried hard to get McCain and Obama to speak directly to the other when it was evident they didn't want to.

During the vice presidential debate, Republican Sarah Palin took pride in not answering Ifill's questions. "She blew me off," a bemused Ifill said later.

The advantages of a town hall style meeting were muted in Brokaw's presidential debate. The longtime NBC newsman was spoofed by his own network's "Saturday Night Live" for overseeing a dry debate: "From this list of penetrating, insightful and provocative questions, I have chosen the eight least interesting," said Brokaw impersonator Chris Parnell.

The "SNL" skit's running gag was about debate rules with time so short that Brokaw cut off the contenders before they could answer a question.

"Why can't we have a debate that allows the candidates to go deeper into the issues and actually engage each other?" wondered Richard Greene, a public speaking coach and author of "Words That Shook the World: 100 Years of Unforgettable Speeches and Events." "At this point the moderator stands in the way and it's the fault of the campaigns for setting up these rules."

The two candidates will sit at the same table for the third debate, so close that will be able to reach out and touch each other. Schieffer hopes this will encourage more interaction.

He's not reluctant to press the men to stay on point.

"It will not embarrass me, if they go off in a different direction, to say `excuse me, could you focus on the question that I just asked?"' he said.

Good luck.

"He'll try," said Vincent Hutchings, a political science professor at the University of Michigan. "But they're pretty good at avoiding that."

It's always a tough call for a journalist in this situation. Do you ask the question, and trust that it's evident to viewers when the candidate is completely ignoring it? Or do you press persistently, taking the risk that your conduct becomes the issue as much as the question itself — as CNN's Campbell Brown found when her questioning of a McCain aide angered the campaign.

Bruce Cain, director of the Washington program for the University of California at Berkeley, said he hoped Schieffer could compel the candidates to speak more specifically about the steps they would take to solve the economic crisis, both short- and long-term.

"We didn't, as many people have noted, hear anything in the (second) debate that we didn't hear three months ago, other than they support the bailout plan," Cain said.

That's not entirely true, as McCain used the forum to discuss a plan to buy the mortgages of struggling homeowners. Making new proposals carry a risk; MSNBC's measurement of what undecided Republican voters were thinking while listening to the debate found an immediate negative reaction to the idea.

To a certain extent, the debates at this stage are almost moderator-proof, Cain said. The candidates have long since figured out what they do or don't want to say, and they've had a year's worth of practice making their points in regular debates.

"It may be that our expectations of what the debates are all about have to be adjusted to reality," Cain said.

Sam Feist, political director at CNN, said he believed the debate's format allows for some flexibility. "It sets the stage for the last debate to be the most interesting of the debates," he said.

Since he knew he would be moderating the debate, Schieffer has been clipping articles and consulting think-tank experts to come up with ideas for questions. He was sitting down to read the transcript of the first two sessions.

When he moderated a Bush-Kerry debate, Schieffer showed up with three times as many questions as he had time to ask. He said he had a nightmare that all of his questions had been used up with a half-hour to go.

He believes the election is still very close and many people will finally make up their minds based on what they see on Wednesday.

"I don't want to think about it too much," he said, "but I think it could very well determine who our next president will be."