This week, California Senate President pro Tempore Kevin de León formally announced his candidacy for the U.S. Senate seat currently held by Dianne Feinstein, who is up for reelection in 2018.

While coverage has centered around de León's criticism of Feinstein for playing too nice with Republicans, not much attention has been given to each candidate's position on the environment. But in the last California Senate race, around 80 percent of voters said a candidate's stance on the environment was "very" or "somewhat" important in determining their vote.

On the surface, it would seem that the two candidates have championed separate causes.

"De León has clearly latched onto environmental issues as something that he cares deeply about, that he's taking a lead on in Sacramento," said Darry Sragow, a longtime Democratic strategist, attorney, and adjunct assistant professor of political science at USC. "He's being very forceful in fostering decarbonization."

Feinstein, on the other hand, has focused on other issues.

"[Feinstein] is a fierce, fierce advocate for protecting the deserts in California," Sragow said.

De León can perhaps boast a more exemplary record across the board than Feinstein. He has authored two major bills — SB 350 and SB 535 — which increase California's use of renewables and benefit communities disproportionately affected by pollution, respectively. He has also supported clean energy upgrades for schools, and enforcement of clean air and water standards.

However, Feinstein is no slouch when it comes to the environment. She has introduced proposals for California desert protection, and has an exemplary voting record on pollutant regulations and endangered species protection, among other things.

Sragow noted the inherent limits placed on Feinstein as a national senator.

"[U.S. senators] have to pick and choose what issues to focus on," Sragow said. "They can care about an issue, but if they're not on the committee that votes on it, they're going to have very little impact."

Sragow suggested that if de León were elected, he would be representing the entire state of California, not just his district, which would likely change his policies.

That is, if he gets elected in the first place. Rarely are long-serving senators like Feinstein ousted, especially by a state senator.

"Feinstein is in very solid shape going into the 2018 election," Sragow said. "She is well-known, she is respected, and she has every reason to think that she's going to win. That said, you can never be sure about much of anything in politics."

Then again, the race is two years out, leaving plenty of time for other candidates to join the mix.

"There are all kinds of rumors about who might run, because politics lives on rumors," Sragow said. "There's talk that Tom Steyer, who's a billionaire with a strong interest in the environment, may run. It's impossible to say, and we're not even talking about the Republicans."