MPR’s Tom Scheck reports on first U.S. Senate debate. Taxes, health care and national security were among the key issues addressed by three candidates running for Minnesota's open U.S. Senate seat. The seat has been viewed as one of the more competitive seats in the nation ever since Mark Dayton announced his decision not to run for reelection. Republican Mark Kennedy and DFLers Amy Klobuchar and Ford Bell all hope to replace the DFL incumbent and put their differences on display in the debate sponsored by the North Metro Chamber of Commerce.