Though it's still relatively early on the campaign calendar, Minnesota's U.S. Senate race has had the kind of high profile that many races don't attain until closer to November. That's largely because the campaigns of DFL incumbent Paul Wellstone and Republican challenger Norm Coleman took to the airwaves with ads months ago. We're likely to see even more of both Senate candidates showing up in television spots through the fall, and that's begun to concern campaign strategists for some of the state's gubernatorial candidates. As the election nears, airtime will become scarcer and the gubernatorial campaigns worry they'll get squeezed out of the picture. Minnesota Public Radio's Tom Scheck reports: