Swing states that played a key role in electing Donald Trump president have posted some of the biggest declines in unemployment during the early phase of his administration. Six states voted for President Barack Obama, a Democrat, in 2012 and then Mr. Trump, a Republican, in 2016: Ohio, Michigan, Florida, Iowa, Pennsylvania and Wisconsin. The median unemployment rate of those switchover states has fallen far faster than the national median this year, according to an analysis of data released by the Labor Department on Friday. The median rate of those states stood at 3.9% as of July, down from just under 5% in December. By comparison, the national median fell to 4.1% in July from 4.7%.