I would think this is more politically risky for Hassan than legalizing marijuana not understanding the logic here she seems all in for this but seemed worried about the political implications of legalizing pot....
She doesn't want to jump the gun and legalise pot before Colorado's and Washington's experiments have been carefully scrutinising. Sure, she could endorse legalisation - and it has tons of support now; but what happens if legalisation turns into a cluster? Then, she'd be the first governor to fully support what amounts to a dud.
When/if legalisaton has no negative effects, Hassan/Brown/O'Malley/Shumlin and the like will throw their support behind legalisation, as if they had been for it all along.
However all sorts of states have banned the death penalty with little negative consequences, so she's "safe" with this call.
