“Denying the basic existence of climate change is no longer a credible position,” said Whit Ayers, a Republican political consultant, pointing out the growing climate concern among millennials as well as centrist voters — two groups the G.O.P. will need in the future.

It is at least partly opportunism, given that some lawmakers are simply reframing longstanding policies or priorities as “climate” policy. Still it is a significant shift, indicating that at least a few prominent Republicans see an advantage to breaking from right-wing orthodoxy that has long dismissed or openly derided concerns about the climate.

In recent weeks Senator John Cornyn of Texas — an oil state where climate denial runs deep — said he is helping write legislation to reduce emissions through “energy innovation.” Senator Lamar Alexander of Tennessee said he wants to create a “Manhattan Project” for clean energy funding. Senator Lisa Murkowski of Alaska is exploring bipartisan plans to curb emissions from her position as chair of the Senate Committee on Energy and Natural Resources. And Representative Matthew Gaetz of Florida, who once called to abolish the Environmental Protection Agency, introduced legislation to tackle climate change by encouraging nuclear energy and hydropower, as well as “carbon capture” technology, which aims to pull planet-warming carbon dioxide out of the atmosphere.