Former Vice President Joe Biden bemoaned the tone of Trump-era politics at a campaign stop in Iowa on Tuesday, previewing on his first trip to the leadoff caucus state how he might take on the Republican president should he seek the 2020 Democratic presidential nomination. “It’s our leaders who need to set the tone and dial down the temperature and restore some dignity to our national dialogue,” Biden said in Cedar Rapids while stumping for Iowa’s Democratic gubernatorial candidate and a House candidate from northeast Iowa. […] Biden quickly pivoted from pleasantries to attacking Trump’s moral leadership, indirectly charging him...