US President Joe Biden's decision to run for re-election was initially clouded by concerns over Vice President Kamala Harris's readiness to face former President Donald Trump, Axios reported on Monday, citing three aides familiar with the discussions.

The chief reasons include concerns about her leadership effectiveness, high staff turnover, and her difficulties in handling politically risky situations.

On Sunday, Biden ultimately chose to step down from the race and endorsed Harris, though his private doubts indicate a broader uncertainty among some Democratic leaders about her viability as the party's nominee.

The upcoming week will be pivotal for Harris as she works to solidify her position and eliminate potential challengers for the Democratic nomination.

While Biden, along with Bill and Hillary Clinton, has publicly supported Harris, other influential Democrats, including former House Speaker Nancy Pelosi, House Democratic leader Hakeem Jeffries, Senate Majority Leader Chuck Schumer, and former President Barack Obama, have yet to fully endorse her.

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Harris' time as vice president has been marked by significant staff turnover and strained relations with the White House.

Many former aides have cited her high standards and demanding nature as factors contributing to the frequent changes within her team.

The vice president's staff turnover contrasts sharply with the more stable staff of Biden during his vice presidency under President Obama.

Tensions between Harris' office and the White House have been noted, with some aides feeling that the Biden team was unhelpful and occasionally obstructive.

Despite these challenges, Harris's chief of staff, Lorraine Voles, stressed the collaborative efforts between her team and the White House.

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