Minnesotans will gather in community centers and schools across the state tonight (TUESDAY) for precinct caucuses. The meetings are the first step in selecting candidates for the 2002 election. In advance of the caucuses, two Republican candidates for governor - Tim Pawlenty and Brian Sullivan - have been running ads to introduce themselves to voters. In the first in a series of Ad Watches, Minnesota Public Radio's Laura McCallum asks an advertising expert to critique the latest spots...