<span style="color: #222222;">Former US Vice President Joe Biden formally joined the crowded Democratic presidential contest today, betting on his working-class appeal and ties to Barack Obama's Presidency. He made this announcement in a video posted on Twitter.</span><br />'' <br />'' <span style="color: #222222;">Biden, a 76-year-old lifelong politician has unmatched international and legislative experience, and he is among the best-known faces in U.S. politics. </span><br />'' <br />'' <span style="color: #222222;">The Republican Party wasted no time seeking to undercut Biden's record, releasing a video yesterday questioning economic growth under Obama and Biden.</span><br />''  <br />