By CNN’s Wolf Blitzer

(CNN) - It’s pretty amazing how significant the Republican presidential debates have proven to be this year. They have clearly shaped attitudes in rather dramatic ways.

Presidential historians may write one day that this was the year of the debate.

There already have been so many memorable moments – many that the candidates would certainly like to forget.

Last night in Michigan may have been the most memorable and awkward debate moment ever.

That was when Rick Perry had a brain freeze for nearly 60 seconds and forgot the third agency of the U.S. government he would like to eliminate, even though he had routinely cited those three agencies in his campaign stump speech (Education, Commerce and Energy).

But there have been several other moments, including that nasty exchange at the CNN debate in Las Vegas between Perry and Mitt Romney over illegal immigrants working on Romney’s lawn, and that moment at the CNN debate in Tampa, Florida, when some audience members applauded and shouted “yeah” when I asked Ron Paul if we should let an uninsured 30-year-old die.

All of which underscores how important these debates have proven to be. Millions of people watch the actual debates, and tens of millions of people wind up watching those one-minute highlight clips.

Perry entered the race for the GOP nomination nearly three months ago with incredibly high expectations. But his poll numbers have collapsed, largely because of his weak debate performances.

In contrast, Romney’s front-runner status has been steady, in part because of his impressive debate performances.

And Newt Gingrich’s recent slow but solid climb has certainly been helped by his debate performances.

The bottom line: If you want to be president of the United States, you better be prepared to debate.

RELATED: Five things we learned from Wednesday's GOP debate

Follow Wolf Blitzer on Twitter: @WolfBlitzerCNN