A few weeks ago everyone knew that the Republican nomination race was between Mitt Romney and Rick Perry. Guess what? That’s still true now. You can safely ignore the polling that shows Herman Cain surging, just as you could have safely ignored previous surges by Michele Bachmann and Donald Trump.

What’s going on this year in Republican presidential politics is, in a way, a fascinating two-track process. On one track is the almost ruthless efficiency with which party actors have narrowed the field, eliminating such once-serious contenders as Tim Pawlenty, Haley Barbour, and Chris Christie, who is expected to announce today that he’s not running. This has left Republicans with two serious candidates, Romney and Perry.

At the same time, there’s a public reality TV show going on at Fox News and elsewhere that has very little to do with the actual business of selecting the candidate. In the GOP Nomination Reality TV Show, different “candidates” get rolled out, get a bunch of attention, get the subsequent polling bump that proves little more than that they’ve been in the news lately, and then everyone gets bored and moves on to the next one.

As the Iowa caucuses get closer, the odds are that the reality show track will shut down, and we’ll be left with the one real battle for the nomination — Romney versus Perry — which by then will include both party actors and rank-and-file voters. It’s possible we may see the reality track make a comeback as other candidates (Santorum? Gary Johnson?) enjoy short-lived media surges. After all, the cable networks have a serious incentive to keep the nomination fight alive as long as possible.

The trick, as always, is to know which is real (presidential politics) and which is reality TV hype. The easy hint: when the Godfather’s guy is surging, fuggedaboutit.