In a surprising move, Maine Senator Olympia Snowe announced on Tuesday that she will not pursue a fourth term in November. One of the three Republicans to support president Obama’s 2009 stimulus package, Snowe cited the senate’s “atmosphere of polarization” as one of the reasons she decided not to run. Her departure is yet another sign that moderates are less influential in D.C. Todd Zwillich is Takeaway Washington correspondent. He explains why Snowe’s retirement is a boost to Democrats. Ron Christie is Takeaway contributor and Republican political strategist.