 In 2016, Hillary Clinton increased the Democratic margin of victory even further.She became the first Democrat to win 60% of Dallas County since Franklin D. Roosevelt in 1944, whilst under Donald Trump the Republicans failed to win 40% of the vote in the county for the first time since 1992.The Democratic gains in the county are primarily due to the exurban migration of disproportionately conservative, Republican-voting residents to the neighboring counties of Collin, Denton and Rockwall As a result, those counties have become more solidly Republican.