Jumping aboard an increasingly popular bandwagon, Democratic presidential candidate Hillary Clinton on Tuesday made her clearest statement yet against drilling for oil in the Arctic Ocean off Alaska.

The tweet came one day after the administration of President Barack Obama granted Shell the final permit it needed to drill deep into the waters off the Alaskan coast—a move that stoked the outrage of green groups nationwide. 

While Clinton expressed “skepticism” about Arctic drilling less than a month ago, her position appears to have evolved since then. The Hill reports: “Her clarified position is likely to bolster her standing among greens, some of whom have previously questioned her focus on environmental issues.”

But her stances on other key climate issues, such as construction of the Keystone XL tar sands pipeline, remain nebulous.

Clinton’s rivals for the Democratic nomination, Bernie Sanders and Martin O’Malley, have clearly stated their opposition to Arctic drilling.