Moments ago, Mitt Romney wrapped up his big speech on the economy. Romney’s heavy emphasis on his private-sector experience was another reminder that he now views the 2012 GOP primary as essentially a head-to-head battle with Rick Perry, the longtime governor of Texas.

New polling out today supports this reading of the contest. And the truth is that the other candidates — the fringe candidates — are rapidly running out of time to change this.

If any of these remaining candidates is serious about trying to change it, we should know tomorrow night at the debate at the Reagan Library. If we see real fireworks, it will suggest that the fringe candidates are still serious about trying to win. But if we don’t see serious attacks, it will be good evidence that the fringe candidates aren’t really seeking the nomination, and that the shape of the contest has now more or less been determined.

Not all debates are equal. This one looms large for several reasons. The Reagan Library debate has become a bit of a tradition, and that, plus the ever-magic Reagan name, makes this one stand out from others in the endless series of Republican clashes. This debate is also notable because it will be new frontrunner Perry’s first time on the stage. On top of that, Barack Obama’s job speech and scheduling flap wound up pushing a bit more publicity onto the event. Put it all together, and this will probably wind up the most-hyped, and therefore most-noticed, debate up until the primaries actually start.

For the two front-runners, Romney and Perry, the obvious debate strategy is to survive without any damage. You probably won’t see them attack each other. Indeed, Romney’s job plan is basically the kind of stuff you expect from a leading candidate: nothing too startling.

For the others, this debate is a good chance to get noticed. And the best way to get noticed is to attack. But who to attack?

The strategic imperative for all the fringe candidates is to take out one of the front-runners. For Jon Huntsman, it’s to knock off Romney and wind up one-on-one against a conservative; for the rest, the obvious target is new frontrunner Perry. So if Michele Bachmann, Newt Gingrich, Herman Cain, Ron Paul, and Rick Santorum still think they can be the nominee, expect them to attack Perry.

If, on the other hand, Bachmann and the rest are really running for the role of Conservative Hero — and not for the nomination — then it makes more sense to just go ahead and attack Romney for his various deviations from the True Faith.

Bottom line: The key thing to watch the fringe candidates for is whether they think they are serious contenders — and what kind of sideshow they will provide during the rest of what really is a two-person race.