Lt. Gov. Dan Mongiardo leads state Attorney General Jack Conway, 37 percent to 30 percent, in the 2010 Democratic Senate primary, according to new polling data on the race to replace retiring Sen. Jim Bunning (R).

Another 15 percent of Democratic primary voters were undecided in the poll, which was sponsored by the liberal Web site Daily Kos.

In the GOP primary, Secretary of State Trey Grayson led anti-tax activist Rand Paul, the son of Rep. Ron Paul (R-Texas), 40 percent to 25 percent with 18 percent undecided.

And although Grayson, the choice of most establishment Republicans, led both Democratic candidates in head-to-head matchups, his 4-point lead over Mongiardo and 6-point lead over Conway are not insurmountable. Grayson topped Mongiardo in the poll, 45 percent to 41 percent, and Conway, 46 percent to 40 percent.

Paul, on the other hand, trailed both Democrats in the general election by small margins. The survey showed Mongiardo defeating Paul, 42 percent to 37 percent, and Conway defeating Paul, 41 percent to 37 percent.

The Research 2000 poll took the opinion of 600 likely state voters from Aug. 31 to Sept. 2 and had a margin of error of 4 points.