For those tuning into tonight’s Republican presidential debate at the Ronald Reagan library in southern Cal, Michael Barone has adroit analysis of the current field.

The good news for Republicans: Obama’s poll numbers are tanking. The bad news for Republicans: they don’t have a clear front runner. No candidates polls better against Obama than does a generic Republican candidate:

It’s easy to see how the debates could become a contest in which each of the two leading candidates attempt to undermine the other’s conservative bona fides. Others, notably Michele Bachmann, whose victory in the Aug. 13 Ames straw poll in Iowa was overshadowed by Perry’s candidacy announcement the same day in Charleston, S.C., have an incentive to do so as well.

The challenge for Perry and Romney, who both have more executive experience than candidate Obama had in 2008, is to show the discipline and focus to establish themselves as serious general election candidates with better ideas about how to jump-start the economy than the hapless incumbent.