Senate Republican Leader Mitch McConnell and Democratic challenger Alison Lundergan Grimes debate for the first (and likely only) time tonight.The debate begins at 8 p.m. and can be seen on KET."This is the only chance that voters of Kentucky are going to have to see a side-by-side non-commercial comparison of the two people who want to represent them in the United States Senate," said Al Cross, a longtime political columnist.The debates are also an opportunity for the candidates—either to persuade fence-sitter or to stimulate enthusiasm among their respective bases, Cross said. (A federal judge has denied Libertarian candidate David Patterson's request to force KETto include him in the debate, by the way.)The "enthusiasm" point is important for both, because Democrats historically have turnout issues in mid-term elections and McConnell still faces questions about his conservative bona fides, Cross added.So what does Grimes and McConnell need to do tonight? Cross said he believes Grimes has the most at stake. Voters aren't as familiar with her as they are with McConnell, and she also took criticismrecently for refusing to say whether she voted for President Obama."She needs to be comfortable, articulate, personable—she needs to inspire confidence," Cross said. "That's what any person seeking high public office needs to do, inspire confidence And the last week or so, she's not done much of that."Dewey Clayton, a political science professor at the University of Louisville, said Grimes must "come across as knowledgeable to the voters, capable of providing fresh leadership, and willing to answer all of the questions she is asked."Also, Clayton said, "She needs to counter any attacks by McConnell that she is an Obama clone—and let the voters know that if elected, she would not be a rubber stamp for Obama but would serve in the best interests of the people of Kentucky.Cross said he believes McConnell is leading the race at the moment. The senator's task, then, will be to "avoid gaffes, avoid damage and try to keep her on the defensive."Clayton said McConnell should remind voters that he's poised to be the next Senate majority leader.But Clayton said he believes McConnell has come across in recent interviews as "stodgy and out of touch," and will want tonight to appear "friendly and engaged." Also, Clayton said: "It is important that McConnell is careful not to come across as condescending to Secretary Grimes. If he is overbearing, that could be a turn-off for voters who may see him as sexist. After all, he is trying to woo female voters and counter attacks by Grimes that he is anti-women."The issues to watch include immigration and healthcare, Cross said. On healthcare, Cross said he'd be interested to see if McConnell says more about his position besides his opposition to the Affordable Care Act. Specifically, Cross said, whether McConnell says what he'd replace the ACA with.Clayton said jobs and the economy will also be interesting issues to keep an eye on tonight.WFPL will have coverage of the debate tonight and tomorrow. Stay tuned.