It's hard to go back home again.  That's what a new poll says about two Minnesotans after their failed attempts at running for president.  The Public Policy Poll shows Minnesota's two U-S senators in good standing among prospective voters.  The latest numbers give Amy Klobuchar a 61-percent approval rating while Al Franken has 49-percent.  Both percentages are high, given the current climate in Washington.  The poll also offers a hypothetical Senate challenge from Michele Bachmann and Tim Pawlenty.  The numbers show both with negative favorability ratings which pollsters say would result in an easy victory for Klobuchar if challenged by either -- and a more narrow win for Franken over Bachmann and Pawlenty.