CNN noticed that Secret Service arrived at Joe Biden’s home in Delaware last night, which makes it almost official.

The case for Joe Biden as Barack Obama’s running mate is simple: he’s got a lot of experience at the federal level, particularly in foreign policy. That will reassure voters who may be concerned about Obama’s resume and blunt a major line of attack from John McCain (whose ads have been questioning whether Obama is “ready to lead”).  

But plenty of people in Washington have served in Congress for 20 or 30 years. What makes Biden better than most of them as a running mate? Media scripts about the “gaffe machine” notwithstanding, I submit that Biden’s campaigning ability will be a huge asset to Obama.

I know the stories about Biden putting his foot in his mouth, and I am old enough to remember the Clarence Thomas hearings, when Biden talked too much and didn’t put Thomas on the spot enough.

But he is a much better campaigner than people give him credit for.

Of all the presidential candidates, Biden got the best word of mouth from Iowans who attended his events last year. I don’t think I ever talked to anyone who went to hear him and walked away unimpressed. I wrote about this last summer and again right before the Iowa caucuses.

If you don’t believe me, read accounts by other people who listened to Biden take questions for an hour or more from voters, sometimes just about Iraq and foreign policy but more often about any topic Iowans felt like bringing up.

Biden is not going to need a crash course in federal policy to prepare for the vice-presidential debate, because he knows this stuff inside-out. And despite his reputation for long-windedness, he is able to answer questions in 30 to 60 seconds. In the Democratic candidates’ debates last year, Biden did extremely well despite consistently getting 30 percent to 50 percent less time to speak than the front-runners. He often had the most memorable one-liners from those debates too.

Speaking about the news media’s blackout of long-shot Democratic contenders, Elizabeth Edwards wrote in this op-ed for the New York Times:

And it’s not as if people didn’t want this information. In focus groups that I attended or followed after debates, Joe Biden would regularly be the object of praise and interest: “I want to know more about Senator Biden,” participants would say.

Biden’s speaking style is more aggressive than Obama’s, which will help him be the attack dog Obama needs.

I also agree with Jonathan Singer’s point that Biden’s relative lack of wealth will reinforce the message that the Democratic candidates can relate to ordinary Americans on bread-and-butter economic issues.

Finally, Steve Clemons is absolutely right: Americans are going to love Jill Biden.

Biden wasn’t my number one choice for Obama’s vice president, but he is going to bring a lot to the table.