"Suppose you had to choose between two Presidential candidates, one of whom had spent 20 years in Congress plus had considerable other relevant experience and the other of whom had about half a dozen years in the Illinois state legislature and 2 years in Congress. Which one do you think would make a better President? If you chose #1, congratulations, you picked James Buchanan over Abraham Lincoln. Your pick disagrees with that of most historians, who see Lincoln as the greatest President ever and Buchanan as the second worst ever, better only than Warren "Teapot Dome" Harding. Both served in what was probably the most difficult period in American history, where slavery and secession tore the nation asunder.

Before becoming President, Buchanan had served 6 years in the Pennsylvania state legislature, 10 years in the U.S. House of Representatives, 4 years as ambassador to Russia, 10 years in the Senate, 4 years as Secretary of State, and 4 years as Ambassador to England. Talk about experience, Buchanan did just about everything except serve on the Supreme Court, a job he was offered by President Polk and refused. Yet by any measure, he wasn't up to the job as President. In contrast, Abraham Lincoln served 8 years in the Illinois legislature and one term in the U.S. House (1847-1849), a decade before becoming President. The rest of the time he was a lawyer in private practice, a bit thin one might say."

http://www.electoral-vote.com/evp2008/Info/experience.html

Obviously this is not hard evidence but it does show how thinking purely about experience without truly evaluating candidates on talent and judgment is a bad idea.