The Republican primary battle for Kentucky's Fourth Congressional District seat isn't a national news story by any means, but observers are using the race barometer of U.S. Sen. Rand Paul's power in the state.From Politico: In this comfortably Republican seat the primary to watch is on the GOP side, where tea party forces are confronting the establishment. Amid the crowded field of candidates, Sens. Rand Paul and Mike Lee are backing Thomas Massie while Davis and former Sen. Jim Bunning, who once held this House seat, are supporting Alecia Webb-Edgington. Massie and Webb-Edgington aren’t the only candidates of note in this northern Kentucky seat – it’s a 7-candidate field -- but they’ve won the most attention because of their high-profile supporters. Since the GOP primary is the first in the state where Paul has put some skin in the game – he cut an ad for Massie that appeared on broadcast and cable television -- Massie’s performance will be closely watched. The results will not only test Paul’s clout, but also signal the mood of Kentucky Republicans in Senate Minority Leader Mitch McConnell’s backyard.