By telling Barbara Walters that she thinks she can defeat President Obama, Sarah Palin has dimmed hopes cherished by sensible Republicans that she might decide against a run for the White House in 2012. Here are just some of the reasons she should not run. The Republican nominee should be someone with a vast and impressive record in government and the private sector. Voters chose a novice with plenty of star power in 2008 and will be inclined to swing strongly in the other direction in 2012. Americans will be looking for sober competence, managerial skill, and maturity — not...