Madison, Wis. (Learfield) - A UW-Madison political scientist says the recall efforts launched against 16 state Senators are unlike anything ever seen before. Professor Charles Franklin says it’s very unusual to see multiple lawmakers targeted for recall at the same time -- let along eight Democrats and eight Republicans simultaneously. Several groups have started collecting signatures on petitions in Senate districts across the state. Their focus is on all 16 members of the state Senate who are legally vulnerable to be recalled at this time. The remaining 17 members of the Senate are not eligible for a recall until at least next year. Before a recall election can actually be set, groups will need to collect signatures equal to 25-percent of the votes for governor cast in that district in the last election. Even if they succeed, Franklin says taking down a sitting senator will not be easy. Of the Senators targeted, Franklin believes only four could be considered vulnerable after their last election because they won with less than 52-percent of the vote. The other 12 had much stronger majorities backing them, greatly reducing the chance voters would side with a new challenger in a recall election.