The Post on the Wisconsin debate: John Edwards sharpened his differences with John F. Kerry on Sunday night in the final televised debate before Tuesday's Wisconsin primary, challenging the front-runner on trade issues and telling him, 'Not so fast' about asserting he will be the Democratic presidential nominee. Although former Vermont governor Howard Dean declined to repeat some of his past criticisms of Kerry's fundraising practices and support of the resolution authorizing use of force against Iraq, Edwards was more personal and pointed in his comments on the senator from Massachusetts than before.