uly 20, 2006 -- THE reverb is still echoing over Dan Quayle's walkout in the middle of a John Mellencamp concert in Lake Tahoe last weekend. The singer-songwriter introduced his tune "Wall Talk" by announcing, "This next one is for all the poor people who've been ignored by the current administration." As Quayle exited, the former veep explained, "I didn't appreciate the comment, and besides, I didn't think the show was very good." But Mellencamp said he couldn't care less that Quayle got his knickers in a twist: "I certainly wouldn't have changed a word." NBA Hall of Famer Charles Barkley backed Mellencamp, saying, "He's right." While that may sound odd coming from a former conservative, Barkley told a local reporter, "I was a Republican - until they lost their minds." Quayle, known for his great golf game, served as veep under President Bush's father from 1989-'93.