I’m just now getting caught up with last night’s Republican candidates’ debate (CNN seldom wins out over Monday Night Football in my viewing selections) and have to say I was impressed by how well Michele Bachmann landed blows against Rick Perry.

Some have asked me why I think Bachmann has fallen off so sharply in many national polls since Perry entered the race. The latest CNN poll, for example, now has her in fourth place. Some surveys show her losing her lead in Iowa. But remember how rapid her rise was after that New Hampshire debate. Many Republicans were looking for a conservative/Tea Party candidate, didn’t think Mitt Romney did the job, and weren’t impressed with Tim Pawlenty as an alternative.

Bachmann burst on the scene and captured the mantle of these voters. But she didn’t have their support nailed down, so she was quickly eclipsed by Perry. Much the same thing happened to Herman Cain, who had a rapid ascent after the South Carolina debate and subsequent fall. Could the same thing happen to Perry, even if there isn’t a late entry like Sarah Palin? That’s what last night’s sustained assault on the Texas governor’s conservative credentials by nearly the entire GOP field was designed to find out.