Here's a tip for presidential candidates: When you say during a debate that you want to get rid of a certain number of government agencies, make sure you can name them all. Rick Perry famously messed that up during his presidential campaign back in 2011 — naming just two of his promised three agencies and finishing lamely with, "Oops."

Now, during Tuesday's Republican debate, his fellow Texan Ted Cruz made a similar mistake — he named five agencies, but could only come up with four. (He repeated the Department of Commerce twice.)

Today, we rolled out a spending plan. $500 billion in specific cuts. Five major agencies that I would eliminate, the IRS, the Department of Commerce, the Department of Energy... [awkward pause as Cruz tries to think of the others] ...the Department of Commerce, and HUD. And then 25 specific programs again, that's on our website at tedcruz.org. You wanna look at specificity? It's easy for everyone to say, "Cut spending." It's much harder and riskier to put out chapter and verse specifically to programs you would cut to stop bankrupting our kids and grandkids.

The agency Cruz couldn't remember, as his website reveals, was the Department of Education. When you want to eliminate so many, it's tough to keep them all straight. Learn more about Cruz's tax plan from Dylan Matthews here.