Many Muslim activists and operatives already felt all but neglected by the Democratic presidential candidates.

Now, as most 2020 contenders are set to skip what is billed as the largest annual gathering of Muslims in the country this weekend, they’re growing increasingly fearful that Democrats may miss an opportunity to mobilize their community against President Donald Trump next year.

Only two Democratic hopefuls, Bernie Sanders and Julián Castro, have confirmed they are going to the Islamic Society of North America’s convention. Organizers said they invited every candidate polling above 1 percent to participate in the presidential forum, as well as Trump, who also is not attending.

“If they’re serious about courting the Muslim vote, they have to show up. They have to actually follow up words with actions,” said Wa’el Alzayat, the CEO of Muslim advocacy group Emgage and a former member of the Obama administration. “They have positioned themselves as the party that has opposed the Muslim ban, rampant Islamophobia, and the rhetoric and policies of the Trump administration.”

The convention, which is being held in Houston, Texas, is expected to draw 20,000 people. Trevor Noah, host of Comedy Central's The Daily Show, will speak.

“We often hear a lot of really nice words when people like Donald Trump go after Muslim Americans,” said Abdul El-Sayed, who ran unsuccessfully in Michigan's 2018 Democratic gubernatorial primary. “But there’s another side to this: You have to come and listen to the things we’re asking of our government if you want to leverage our pain.”

For months, Muslim Democrats have raised concerns that the presidential candidates have not paid enough attention to their issues. Trump’s travel ban was discussed for less than two minutes during the primary debates, and activists argue it doesn’t come up much in candidates’ stump speeches.

In recent years, Muslims have worked to prove that they are an increasingly powerful voting bloc that should be taken seriously, particularly in key swing states. Muslim voters were credited with helping Sanders defeat Hillary Clinton in a shocking upset in Michigan’s primary in 2016. According to a study by Emgage, voter turnout among Muslims also increased 25 percentage points between 2014 and 2018 in the states of Ohio, Florida, Michigan and Virginia.

Muslim operatives praised Sanders and Castro for attending, adding that the Vermont senator in particular has done significant outreach to Muslims. Sanders’ campaign manager, Faiz Shakir, is Muslim.

Some Muslim activists believe candidates are giving them short shrift because they employ too few Muslims: “The entire system is rigged to keep our issues out of the spotlight when it’s inconvenient,” said Alzayat, whose group Emgage helped organize the convention.

Others worry that it’s due to fear of turning off voters with Islamophobic beliefs.

“For many politicians, I think it’s not tradition for presidential candidates to go attend large Muslim gatherings. Many political operatives believe Muslims are a liability,” said Linda Sarsour, a high-profile Muslim activist and surrogate for Sanders. “In 2016, Hillary Clinton did one single event that had anything to do with Muslims, and it was in fact about national security.”