Several California cities — including two in the Bay Area — have joined a state lawsuit challenging the Trump administration’s decision to include a citizenship question in the 2020 Census for the first time in 70 years.

Fremont, Oakland, Stockton, Long Beach, and the city and county of Los Angeles on Friday announced they joined the lawsuit, arguing, “An accurate population count of all individuals – regardless of citizenship status – is mandated every ten years under the U.S. Constitution.”

Attorney General Xavier Becerra filed the lawsuit in March, saying the decision to ask participants about their citizenship status is illegal.

“California’s fight to secure an accurate census of our nation’s vibrant and diverse population has just been bolstered by our cities and counties,” Becerra said in a statement Friday. “Together, we will see to it that this sacred responsibility is met by our federal government.”

But supporters of the Trump administration point out that less sweeping surveys like the American Community Survey have continued to ask about citizenship in recent years.

The most long-term impact of a California undercount would be the state’s representation in Congress. Every 10 years, the number of representatives per state is adjusted based on census results, taking into account the state’s total population, including undocumented people. If the census counts fewer Californians, it could mean the state would get fewer than its current 53 House of Representatives members starting in the 2022 elections.

“It is no secret that the Trump administration is dead set on reducing the voting power and federal funding for states like California and cities like Oakland whose residents overwhelmingly did not cast their votes for the current occupant of the White House,” said Oakland City Attorney Barbara J. Parker in a statement Friday. “The addition of a citizenship question clearly is a pretext for achieving that goal. Faced with the loss of the popular vote and a country that has an increasing number of immigrants and people of color, this outlaw administration is attempting to undercount and disenfranchise diverse communities like Oakland and California.”

Fremont city attorney Harvey Levine said that since federal programs rely on the Census count, “our community will be cut off from funding intended for the most needy and vulnerable among us.”

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The question was originally requested by the Justice Department, which said it uses the information to “protect voters against racial discrimination.” Every Census since 1965 has included a citizenship question, with the exception of the 2010 Census, DOJ spokesman Kerri Kupec said in a statement Friday.

“The Census Bureau continues to ask a citizenship question, but in recent years has moved that question to the American Community Survey, which—as the Census Bureau itself has recognized—is not the most appropriate data to use as a basis for redistricting,” he said. “The Justice Department looks forward to defending the reinstatement of the citizenship question, which will allow the department to protect the right to vote and ensure free and fair elections for all Americans.”

Staff writer Casey Tolan contributed.