In an effort to give politicians and voters another way to interact, YouTube will get U.S. presidential candidates to post videos on its news and politics site, and let the common folk post their own video responses. This is part of YouTube's "You Choose '08" plan, which hopefully will engage people and - even better - get them to vote. First up to the plate will be ex-Massachusetts Gov. Mitt Romney, who will answer the question: ”What do you believe is America’s single greatest challenge and what would you do to address it?”