Immediately following President Donald Trump’s first State of the Union address on Tuesday night, Senator Bernie Sanders was staring into a video camera, wearing his usual exasperated frown. “Tonight, he avoided some of the most important issues facing our country and the world,” he said about Trump. “How can a president of the United States give a State of the Union speech and not mention climate change?”

Sanders had a right to be frustrated with the president. Record-breaking hurricanes, extreme flooding, and raging wildfires wreaked emotional, economic, and environmental havoc on America last year. Each of these horrors were fueled by climate change—a problem caused by humans, but which is also fixable by humans, if there’s the political will. And yet, Trump didn’t even mention it. He spoke of the year’s record-breaking weather events as if they were merely occasions for American heroism, while promoting the proliferation of our dirtiest energy source.

But if Sanders should be angry at anyone, it’s the Democratic Party. His speech, broadcast on his Facebook page, was one of five rebuttals of Trump, only three of which mentioned climate change—the others being Congresswoman Maxine Waters, who gave her response on BET on Wednesday night, and former Congresswoman Donna Edwards, who spoke on behalf of the Working Families Party. The official response to Trump from the Democratic Party, by Congressman Joe Kennedy of Massachusetts, didn’t mention climate change once. Neither did Virginia state lawmaker Elizabeth Guzman, who gave the Spanish-language response. The same goes for most elected Democrats who responded to Trump’s speech on Twitter and in the media. Even Sheldon Whitehouse, the Senate’s most aggressive climate hawk, ignored climate change in his press statement.

After some of these omissions were reported by HuffPost, Breitbart erupted in glee. “‘Climate change’ just officially ceased being an important issue in U.S. politics,” the far-right site declared. “#Winning!” That’s obviously not true; climate change remains an important issue in U.S. politics, and in Americans’ lives. And yet, the Democratic Party still considers it an optional topic of discussion—even after Trump spent his year ripping climate policies to shreds. If Americans want to hear about that from elected Democrats, they have to turn on BET at 10 p.m. or watch a Facebook livestream.

But the Democrats’ omission not only allows climate-change deniers to falsely claim victory; it also alienates the growing number of voters motivated by climate change, especially within the Democratic Party. A Kaiser Family Foundation poll last week found that Democratic voters ranked climate change sixth among the top issues in the coming midterm elections. As Pew Research reported on Monday, “Nearly seven-in-ten Democrats (68%) say dealing with climate change should be a top policy priority, 50 percentage points higher than the share of Republicans who say so (18%).”