A divisive Republican nomination fight will benefit the Democrats

RAND Paul, the libertarian Republican senator from Kentucky, announced on Tuesday that he will run for president. He is the second major Republican candidate within two weeks to officially declare his intention to enter the 2016 race following the earlier announcement by Texas Senator Ted Cruz, the Tea Party favourite.

Although general election day remains over a year and a half away, Mr Paul's announcement is the clearest sign yet that the Republican field is beginning to mobilise to r…