Former Vice President Al GoreAl GoreHow to make climate progress with Trump in the White House Trump's EPA pick will make Obama regret his environmental overreach Trump’s popularity spikes, but lags behind past presidents MORE on Sunday endorsed Hawaii Sen. Brian Schatz’s (D) reelection bid, citing his work on clean energy and climate issues.

Gore said Schatz’s support for Hawaii’s Clean Energy Initiative had helped the state triple its renewable energy production.

“We’re going to need Brian’s strong, outspoken leadership in Congress for many more years to get the job done,” said Gore in a statement, praising Schatz’s commitment to climate concerns, reports said.

Schatz was appointed by Gov. Neil Abercrombie (D) to fill the seat of the late-Sen. Daniel Inouye (D-Hawaii) after his death in December 2012. Inouye, though, penned a letter shortly before his death asking that Rep. Colleen Hanabusa (D-Hawaii) be tapped as his successor.

Hanabusa is challenging Schatz in the Democratic primary, leaving the freshman senator facing a tough fight.

A poll for EMILY’s List, which has endorsed Hanabusa, showed her with an 11-point lead in a poll of likely Democratic voters conducted in early June.

A poll for the Schatz campaign though found the two candidates each with 37 percent support in early July. 

Schatz has also picked up the endorsement of key labor unions in Hawaii, a critical edge in the Democratic state.