The League of Conservation Voters endorsed Democratic Rep. Patrick Murphy in his Senate race Tuesday, just weeks before the Democratic primary in the Sunshine State.

Murphy is up against Rep. Alan Grayson in the Democratic primary to challenge Republican Sen. Marco Rubio for his spot in the Senate in November. Tiernan Sittenfeld, senior vice president of government affairs for the League of Conservation Voters Action Fund, said Murphy is the Democrat with the best chance of taking down Rubio.

"From recognizing that we have a moral obligation to act on climate change to his commitment to advancing clean energy solutions, we are confident Murphy will be a key voice in the Senate for our environment for years to come," she said.

Murphy is trailing in a head-to-head match up with Rubio, according to the average of polls done by RealClearPolitics. Rubio is up 44.6-40.3 percent, the website reported.

However, Murphy says he plans to hit Rubio on his anti-environment votes in the Senate and called the incumbent senator a climate change doubter.

"Unlike Marco Rubio, I'm committed to showing up and fighting every day to protect our environment in the U.S. Senate," he told reporters.

He said Rubio has ignored the signs of climate change in their home state and has refused to act on solutions despite the potentially devastating impacts it could have on Florida. Many scientists blame the burning of fossil fuels for causing climate change and the subsequent warming of the globe.

Murphy said he would work to prohibit offshore drilling off Florida's coasts and reduce the amount of fracking taking place in the country. Fracking, or hydraulic fracturing, is the practice of injecting water and other chemicals into layers of rock to free up oil and natural gas trapped within.

"Right in Marco Rubio's backyard, high tides are flooding the streets and he refuses to acknowledge something is happening," he said.