Symone Sanders, chief spokesperson and a senior adviser to Kamala Harris, is to leave the White House at the end of the year, Politico has reported, renewing speculation of chaos and dysfunction within the vice-president’s office.

The departure of Sanders is the second high-profile exit from Harris’s staff within two weeks, following the resignation of communications director Ashley Etienne.

It also comes amid reported friction with Joe Biden’s team over the role of his vice-president, and stories that Harris feels “sidelined” in the job as the president prepares to launch his campaign for a second term.

Sanders, in a farewell note to staff reported by Politico, gave no reason for her exit, and did not say where she intends to go next.

Some political observers, however, noted that the news of her leaving came the same day as Stacey Abrams, another highly visible Democrat on the national stage, launched her campaign for Georgia governor.

Sanders, 31, joined Harris’s office after spending the 2020 presidential campaign as a senior adviser to Biden. The former political commentator has been one of the best-known faces in the administration, and a vocal defender of Harris in recent weeks and months as the vice-president faced criticism, particularly after a rocky trip to Guatemala in the summer.

Harris, plagued by the same sinking approval ratings that have plagued Biden, has struggled with messaging, and drawn flak from prominent figures on both wings of the Democratic party, including the moderate West Virginia senator Joe Manchin and the progressive congresswoman Alexandria Ocasio-Cortez.

This contributed to mounting frustration among Harris’s team, and from the vice-president herself, who has reportedly told aides that she feels badly positioned to take over from Biden, even as the 79-year-old president mulls whether to run again in 2024.

Conversely, according to CNN, Biden’s staff is watching closely for any signs of disloyalty within the Harris camp, despite outward messages of support.

Such stories of tension between the two prompted the White House press secretary Jen Psaki to issue a rare defense of the vice-president last month, calling Harris, the first woman and person of color to reach the office, “a bold leader”, and suggesting at least some criticism of her was rooted in sexism.

In a statement to the Washington Post, a spokesperson for Harris paid tribute to Sanders.

“Symone has served honorably for three years. The president and vice-president are grateful for Symone’s service and advocacy for this administration. She is a valued member of the White House and a team player – she will be missed,” it said.

Sanders previously served as press secretary to the Vermont senator Bernie Sanders during his 2016 campaign for the Democratic party’s presidential nomination that year, which was ultimately won by Hillary Clinton.

She became a regular political commentator and analyst on CNN and elsewhere before joining Biden’s team as an adviser and strategist for his 2020 defeat of Donald Trump. After becoming Harris’s chief spokesperson, she traveled often with the vice-president and was quick to highlight her work despite evidence of escalating dysfunction among her staff.