A new survey from Public Policy Polling finds Pennsylvania's Senate race tied, with Pat Toomey and Joe Sestak at 41 percent each, and 18 percent undecided.   Mr. Sestak, the Democratic congressman led in one Rasmussen survey in May, but Mr. Toomey, the Republican, has been the leader in the consensus of polls in recent months.  The poll supports the view that there's lots of opportunity for movement in this matchup as neither candidate has a fully formed public profile at this early stage.  The favorable/unfavorable numbers for each candidate are about even _ 29 percent/28 percent, for Sestak, and 30 percnet/28 percent for Toomey, with big pluralities  not prepared to express an overall opinion on either contender.