BURLINGTON, Iowa (AP) – Joe Biden is anchoring his presidential campaign around questions of character – both his and President Donald Trump’s. The recent back-to-back mass killings in Texas and Ohio have given Biden new traction for his arguments. Biden has spent the past three months largely on defense over a long policy record that draws fire from Democratic Party’s most progressive corners. But he reasserted himself this week with a blistering takedown of Trump’s racist language and the ways in which some of the president’s anti-immigrant outbursts could have inspired one of the shootings. In Iowa, Biden weaved between hushed disappointment and incredulous fury over a president who offers “no moral leadership.”