It’s been several weeks since the candidates all got together, and in the interim the dynamic of the race has changed greatly. Newt Gingrich is now a real force in the race. Texas Gov. Rick Perry has slid so far down, he’s much closer to Rick Santorum than to Mitt Romney in national and many state polls. Herman Cain’s entire public persona has been transformed. And through it all, there is Romney, bobbing along on the waves, never capsizing but never pulling away.

The question on everyone’s mind, of course, is what Herman Cain will be asked and how he will respond to queries about the story that’s dominated the news for over a week. It seems inconceivable that the topic of sexual harassment accusations against him and his handling of the serial revelations would be unaddressed. More interesting will be how much time is allotted and how probing the questions are, and whether Cain calmly responds or becomes annoyed and tries to move on.

In my view, it seems he needs to respond to several aspects of the controversy: Why has his story changed multiple times? Why should we have confidence in either his management skills or his credibility in light of this? How is it possible that five women, two of whom received sizeable payouts long before he decided to run for president, are all wrong or lying? Why is he now playing the race card?

At some point the moderators will be forced to move on. There surely is much ground to cover.

Since the last debate Perry has unveiled his economic plan. It’s important to ask him, for example, why the optional flat tax doesn’t complicate the tax code and why he left out virtually all details on the spending cut side. And yes, since there is much evidence that such a scheme is simply unworkable, he should be quizzed about his plan to let cities and states opt out of Social Security. Finally, we have had a great deal of talk about crony capitalism; Why doesn’t his own record — from the Trans-Texas Corridor to the tech funds to his relationship with lobbyists — suggest he’s been part of the problem?

For Romney, moderators will no doubt press him on his fiscal plan. How is he going to weather Mediscare opposition better than Rep. Paul Ryan (R-Wis.)? Why not sweep away public Medicare altogether? On other fronts, he should be pressed on why he doesn’t yet have a comprehensive tax plan and just how he plans to avoid a trade war with China.

As for Gingrich, it’s time to explore his own record and ideological journeys. Does he think Bill Clinton stole his lunch money? Why did GOP House members revolt under his leadership? Why do his former colleagues recall those years so unfavorably? What does he believe on global warming? He’s always been an internationalist but now he’s saying Libya was a mistake and we should “rethink” Afghanistan, among other things. What does he mean by all that?

And let’s not forget that Cain has raised, aside from his personal issues, numerous questions on his incoherence on abortion and his confusion over China’s nuclear capability,

There are, for all the candidates, a number of topics that really haven’t been addressed in a debate setting: the Second Amendment, selection of judges, defense spending and the federal role (if any) in education. It makes little sense to replow again and again some of the same ground we’ve trudged through already. By now we know all the candidates hate Perry’s tuition tax breaks for illegal immigrants. We all know Rep. Ron Paul (R-Tex.) is a goldbug. And we know Rick Santorum really, really doesn’t favor gay marriage. So let’s not waste time and instead find out what we don’t know about the candidates. That’s what debates, after all, are about.