Although the US Supreme Court's split of 5-4 to issue the stay shouldn’t be read to equate to votes to ultimately uphold the Clean Power Plan, it does provide guidance. As a result, any Obama administration nominee may have to pass a Clean Power Plan litmus test given the administration's clear support of the Clean Power Plan and pledge to limit global warming under the 21st Conference of the Parties (or COP21) agreement. COP21 was the 21stmeeting of the parties to the 1992 United Nations Framework Convention on Climate Change. The agreement reached at the COP21 aims to keep the increase in global average temperature to a maximum of 2° Celsius, but to try to limit the increase to 1.5° Celsius or lower. The Clean Power Plan figures prominently in the US' pledge under this agreement.
The DC Circuit Court denied requests to stay the Clean Power Plan, but ordered an aggressive, expedited briefing schedule to be able to hear the case on June 2, 2016. Opponents then sought, and received the stay from the US Supreme Court. The US Supreme Court's stay remains in place until it issues a decision should it agree to hear an appeal of the DC Circuit Court's decision.
Many anticipate that the DC Circuit Court will decide the legal merits of the Clean Power Plan this fall. If a successor to Justice Scalia is not named before the US Supreme Court is asked to decide an appeal from the DC Circuit Court, the DC Circuit Court's decision would stand in the event of a US Supreme Court 4-4 split.