A Kentucky Farm Bureau candidate forum during the state fair would be lively and well attended, but it's no substitute for the kind of exchange voters are entitled to between this year's candidates for U.S. Senate. KET, Kentucky's statewide public television network, is the best venue for such an event, having filled that vital role for decades. Five-term incumbent Republican Sen. Mitch McConnell has yet to respond to KET's invitation to appear on Kentucky Tonight Oct. 13, while his Democratic challenger Secretary of State Alison Lundergan Grimes has agreed to the joint appearance, which the network bills as a forum moderated by host Bill Goodman. On Wednesday, McConnell challenged Grimes to appear with him during a Farm Bureau candidate forum in Louisville in August. No matter how the Farm Bureau event turns out, McConnell owes Kentuckians a side-by-side comparison on KET.