DFL CANDIDATES FOR GOVERNOR DEBATE EACH OTHER THIS EVENING. THE MINNESOTA NEWS NETWORK IS HOSTING THIS EVENING'S DEBATE AT 6 O 'CLOCK. MOST POLLS SAY ATTORNEY GENERAL "SKIP" HUMPHREY IS THE FRONTRUNNER IN THE ELECTION. SO TODAY, PARTY ENDORSEE MIKE FREEMAN LAUNCHED AN ASSAULT ON HUMPHREY. MPR'S POLITICAL EDITOR BOB COLLINS HAS THAT AND MORE IN THE DAY IN POLITICS. Democrats have tried to avoid a divisive primary campaign which would only help Republican Norm Coleman in November. That may be changing with Mike Freeman's ad campaign against Humphrey. His ads attempts to link Coleman and Humphrey. Coleman, a former Democrat, worked for Humphrey in the Attorney General's office. Freeman p