Democratic White House hopefuls are campaigning in the more than two dozen Iowa counties that went from supporting Barack Obama in 2012 to supporting Donald Trump in 2016. They hope showing up in counties Democrats lost will help prove they can take on the Republican president this year. Their visits may also help Democrats win back these counties in November by energizing Democrats and engaging disaffected Republicans. And they hope to win some delegates by focusing on these counties across the state. Iowa is home to more counties that pivoted from Obama to Trump than any other state.