You might have seen our earlier profile on St. Louis University law prof Joel K. Goldstein, probably the nation’s leading scholar on vice presidents.

He literally wrote the book on vice-presidents, and his working on a second one.

Since we wrote about Goldstein in June, he has been quoted countless times in the national press, including publications such as the Los Angeles Times, Dallas Morning News, the Wall Street Journal, and, just yesterday, the Chicago Tribune.

In an e-mail, Goldstein gives us a custom take on Barack Obama selecting Joe Biden as his veep nominee — and what it might mean for GOP rival John McCain.

Says Prof. Goldstein:

There’s never a perfect choice; presidential candidates choose between human beings with strengths and weaknesses, not between ideal types.

Considering the options Sen. Obama had, I think the Biden choice is a good one.  He’s obviously a plausible president by virtue of his service and leadership in the Senate.  He is popular with colleagues on both sides of the aisle so reinforces Obama’s theme of working in a bipartisan way.

He is likely to have appeal to working class Democrats and to be willing and able to attack the Republican ticket, thereby letting Obama remain above the fray. A chief risk is that Biden sometimes says things which he probably regrets saying the second they are out of his mouth.

Although most emphasis has been on the national security credential Biden brings to the ticket, the economic populism may be more significant.

Biden’s modest roots and life style may make it more difficult for Sen. McCain to select Governor Romney, particularly after the not knowing how many houses he owns episode.  You can just imagine the commercials in blue collar areas that the Republican ticket owns enough houses to fill a gated community.