ST.PAUL FOR USE THURSDAY MORNING, DURING M.E. The latest Minnesota Public Radio--St. Paul Pioneer Press--KARE-11 Television Poll, shows about HALF of Minnesota voters think Republican Senator Rod Grams is doing an execellent or good job and about HALF beleive Democrat Paul Wellstone is going an excellent or good job. But Wellstone has FEWER supporters when it comes to his potential presidential bid. Minnesota Public Radio's Karen-Louise Boothe reports: Grams' over-all approval rating of 42-percent saying he's performing well, compares with the 39-percent he got last JULY. Wellstone's rating of 48-percent compares with his previous rating of 45-percent. St. Olaf Political Science Professor, Dan Hofrenning (HOFF-ren-ing) says the increases a