The fight to protect the Missouri River by the Standing Rock Sioux Tribe is a fight for justice for all of us. The Native-led movement to stop the Dakota Access Pipeline is the largest show of unity and grassroots power in our history, and a key moment that we cannot afford to let pass.

Hundreds of thousands of people nationwide have followed the struggle, with many speaking out on the need to protect land, water, tradition and Native American sovereignty.

But a voice is missing, a voice that in the past has spoken plainly and thoughtfully in support of racial and gender justice, for fairness and equity, and protecting the environment. In her silence, presidential candidate Hillary Clinton is missing a pivotal political moment to take an unequivocal stand for people and planet – and against corporate greed – that many of us on the left have been watching and waiting to see.

Tension is growing and police brutality is escalating at Standing Rock. Our country has a sad tradition of prioritizing corporate need and greed instead of honoring our commitment to Native people. Clinton has a unique opportunity to take a stand on the right side of history.

This week young people from the Standing Rock Sioux Nation called on Clinton, traveling to her campaign headquarters in Brooklyn, New York, asking her to “Stand with Standing Rock” to stop the Dakota Access pipeline.

They delivered a letter from the youth of the Standing Rock Sioux Tribe to Clinton that was accepted by her staff:

“Thousands of Native Americans from more than 300 tribes spanning the continent have joined with us to stand against this violation of the tribe’s rights under federal laws and regulations. Twenty-one city and county governments have also joined us to stand in opposition to this pipeline, and now we need a commitment from you. We demand this pipeline be stopped. It is our land, it is our water, it is our future.

“Now is the time to prove your commitment to both strong climate action and Indigenous sovereignty. Silence is not acceptable, stand with us and oppose the Dakota Access Pipeline.”

In a lukewarm response, Clinton’s campaign staff issued a statement that is at best neutral, and at worse, is shallow and dismissive:

“... it’s important that on the ground in North Dakota, everyone respects demonstrators’ rights to protest peacefully, and workers’ rights to do their jobs safely.”

Clinton has effectively ducked the pipeline controversy throughout her campaign, helped perhaps by the Obama administration’s quick response to a court decision in early September that would have allowed work on the pipeline to proceed. On the heels of the court decision, the Department of Justice and the Army Corps of Engineers suddenly issued a surprising joint letter asking Energy Access Partners to suspend work on the pipeline:

“This case has highlighted the need for a serious discussion on whether there should be nationwide reform with respect to considering tribes’ views on these types of infrastructure projects.”

Energy Access Partners has pushed ahead with construction bringing the pipeline within a few miles of the Missouri River and the Oceti Sakowin Camp. Instead of allowing the U.S. Corp of Engineers to do the proper environmental impact study, the company and the state of North Dakota forcibly removed the prayer camp, injuring many, shooting rubber bullets and forcing a violent confrontation.

President Obama, you must step up and order the State of North Dakota to stand down, put Department of Justice officials on the ground and order the Corps of Engineers to deny the easement to protect the Missouri River from destruction.

But it’s also time for Clinton to publicly weigh in on the debate. The youth of the Standing Rock Sioux Tribe have offered her a precious opportunity – but time is short. Her neutrality is not acceptable, especially when her opponent in the presidential campaign has been vocal and unwavering in his pledge to scrap regulations protecting natural resources and lands, and supporting corporate greed over the health and welfare of every family in America.

Donald Trump has deep financial ties to the pipeline, his presidential campaign has accepted a $100,000 donation from the CEO of the pipeline company, and he has at least a half-million dollars invested in the project.

Asking Clinton to take a stand is not a stretch, and there should be no mystery where she stands. As a senator, Clinton advocated for tough clean water and energy regulations. She co-sponsored legislation repealing subsidies to oil companies. She has a solid position and track record. Yet here she is, in the last days of her presidential campaign, still missing out on the opportunity to voice her position on one of the most visible environmental issues of the moment.

Clinton has an opportunity, and she must grab it, to show that she won’t tolerate corporations trampling on the rights and traditions of Native Americans, or any people in America – and that she won’t allow corporations to destroy precious water, our air, or sacred lands, whether that is a Native American burial site or our national forests.

The young people of the Standing Rock Sioux Tribe conclude their letter:

“As President Obama rejected the Keystone XL Pipeline, we urge the new President to be a leader and continue standing up for what is right by rejecting the Dakota Access Pipeline. The First 100 Days is a significant time for you to set the stage – are you with us?”

The families at Standing Rock deserve an answer. It’s also a question candidate Clinton should clear up quickly for everyone poised over their ballot. Are you with us?