<p>DES MOINES -- Hillary Clinton often says she has learned from the mistakes of 2008 -- and perhaps her biggest test will come tonight at the Jefferson-Jackson dinner, the high-stakes event that launched President Barack Obama’s campaign into the stratosphere eight years ago.</p><p>Clinton rallied her supporters with a shouted “We are geared up and ready to go!” at a rally here Saturday afternoon -- at a parking-lot pep rally featuring her husband and pop star Katy Perry.