Sen. Joe Biden has never had a problem talking. It's stopping talking, say even some of his pals, that's the issue. So much so that when he junked his last presidential campaign and Sen. Barack Obama emerged, some floated Biden's name as a potential secretary of state, in part because he chairs the Senate Foreign Relations Committee and is a very comfortable on the world stage. But it was dismissed by other Democrats who thought the popular Delaware senator's wordy style and knack for sometimes saying the wrong thing was less than ideal for the world's top diplomat. So why would Obama consider Biden as a vice presidential choice? Well, in a word, say Democratic sources, because of his mouth. The thinking is that Biden could take on Sen. John McCain's Straight Talk Express with his own blunt style while allowing Obama to continue his more thoughtful and cerebral style. Here's how one Senate insider explains it: "What may hurt you in one job helps you in the next. In other words, his outspokenness is exactly what Obama needs on the trail and in office. You need a partner who can say the things you can't, who can shoot and still take the incoming fire. Not only can Biden do that but he's good at it. Second, you need to build a firewall to inoculate Obama against criticism. What is the No. 1 criticism against Obama? That he's not seasoned and does not know enough about foreign policy. With Biden, that criticism is DOA. And third, if McCain and Biden have a good history, how ridiculous does McCain look going back and attacking his colleague?"