The Women’s March announced Thursday that Sen. Bernie Sanders (I-Vt.) will address attendees of The Women's Convention on its opening night Oct. 27 — and some activists weren’t happy.

Why was Sanders chosen to speak?

Tamika Mallory, co-founder of Women's March, told USA Today that Sanders was chosen to be a headline speaker at the convention because he knows how to mobilize young activists.

"I think that right now, no one can deny that Bernie Sanders is probably one of the most powerful U.S. senators ... on progressive issues, women’s issues, mobilizing millennials. He is really in line with the principles of the Women's March," Mallory said.

Mallory added that "we believe as women ... that we ought to have more than just women at the Women's Convention."

"People want to hear from the leadership from within our government who can give us some insight about what's happening ... so we can know what we need to do to be able [to] organize," Mallory said.

Sanders wrote in a Facebook post that he is honored to join the event.

“In January, millions of women came out in an extraordinary and unprecedented display of power and resistance,” Sanders wrote. “Now more than ever, we must support the leadership of women across the country and fight together to advance our progressive agenda.”

What did activists say?

Some activists objected to the prominent position Sanders was given at the three-day convention because he is a man, or because he challenged former Secretary of State Hillary Clinton in the Democratic presidential primary.

How did the Women’s March respond?

In response to the backlash, the Women’s March organizers posted a statement on Twitter saying that they invited a number of lawmakers to speak, and that Rep. Maxine Waters (D-Calif.) will also address the convention.

The Women's March added that more than 60 women will address the convention.