The Republicans placed keynote speaker Chris Christie after Ann Romney last week, and he suffered somewhat by comparison. Julian Castro certainly must be very relieved he wasn’t slotted after Michelle Obama last night. His keynote was, for the most part, relatively forgettable anyway, but she totally dominated day one of the Democratic National Convention.

Of course, and with all due respect to Michelle Obama and her speechwriters for a terrific job…it’s hard to go wrong. Before the conventions, I predicted that the presidential and vice presidential speeches would go well because they always go well and they should always go well; after all, you have a huge hall of your supporters just ready to explode; you have all the stagecraft and technique that money can buy; and you have months to write the thing. It’s true that the nominees’ spouses might not be great natural speakers and almost certainly don’t have as much practice and training as the politicians. But they have another advantage — they’re essentially untouchable. Yes, Republicans vilified Hillary Clinton in the 1990s, Democrats did the same to Nancy Reagan in the 1980s, and Republicans have in some cases made up elaborate theories of Michelle Obama as the source of all evil. But while attacking a first lady might be appealing to the most extreme partisans, it just sounds harsh and bitter to everyone else. So the nominee’s wife has almost a free pass.

To be sure, Michelle Obama exploited that fully, painting a picture of Barack Obama, real person, that was in stark contrast both to the image of an America-hater (or at least American-dream hater) that we heard last week, but also to Mitt Romney’s life story. It was, no question about it, effective.

Will it matter to the campaign? Most likely very little. Conventions are very good at transmitting the party’s views to partisan voters who ignore politics most of the time, but with an incumbent president there’s less to do. Almost everyone who is likely to vote for Barack Obama this year already knows who he is and is already planning to support him. And for those who might do more than vote but need a little nudge, odds are that they themselves would fill in whatever was missing in the speeches and images they’re seeing from Charlotte.

So, yes, Michelle Obama was excellent, and the whole first day, as far as I could tell, was as effective as these things can be.But don’t get carried away; good convention nights will evaporate as soon as there’s a bad one, and even a great convention isn’t going to do all that much more than a mediocre one.