AN OBJECT LESSON IN VETTING…. No matter what happens tomorrow, I’d like to think presidential campaign have learned a valuable lesson about the importance of vetting. That’s obviously the case when it comes to running mates — John McCain had no idea who Sarah Palin was before putting her on the national ticket — but it’s also true when it comes to picking mascots to exploit.

Sam “Joe the Plumber” Wurzelbacher asked Barack Obama a question a couple of weeks ago, and according to the McCain campaign, quickly became the single most important person on the planet. McCain didn’t know anything about the guy, but Obama told him he’d like to “spread the wealth” around to the middle class, and as far as the Republican ticket was concerned, that’s all they needed to know. Wurzelbacher became the central focus of a McCain debate strategy, ad campaign, stump speech, and multi-state tour.

And yet, Wurzelbacher’s penchant for saying insane things suggests McCain probably should have thought this through before acting. Yesterday, McCain’s mascot told Fox News that “greatly” questions Obama’s “loyalty to our country.”

This came five days after Wurzelbacher endorsed the idiotic idea that a vote for Obama would be “a vote for the death of Israel,” and four days after Wurzelbacher said the notion of progressive taxation is “honestly right out of Karl Marx’s mouth. No one can debate that. That’s not my opinion. That’s fact.”

Josh Marshall noted that, as far as the Republican ticket is concerned, Wurzelbacher has “become a part of McCain’s campaign, like any other surrogate.” That’s true, but it also goes further — just a few days ago, McCain described Wurzelbacher as “an American hero, a great citizen of Ohio and my role model.”

Role model.”

In other words, the Republican nominee for president has picked some strange man who believes bizarre things and, without any vetting at all, made him the centerpiece of his entire campaign.

Let this be a lesson for all future presidential campaigns: vetting is your friend.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.