A SurveyUSA poll has Rand Paul leading Kentucky Secretary of State Trey Grayson 42 percent to 27 percent in the race for the Republican senatorial nomination. On the Democratic side, Kentucky Lt. Gov. Dan Mongiardo has a similarly imposing lead of 45 percent to 27 percent over Attorney General Jack Conway. The SurveyUSA result for the Republicans isn’t much different than what Public Policy Polling found in December, with Paul leading by 19 points. But it is a big difference for the Democrats — the earlier poll showed Conway leading by four. SurveyUSA shows the race to replace retiring Sen. Jim Bunning could be competitive, since 43 percent prefer a generic Republican and 42 percent want a generic Democrat.