The embattled Biden campaign tests Kamala Harris' strength vs. Trump

President Biden's campaign tests Kamala Harris against Trump as pressure mounts for Biden to step aside. A high-stakes news conference looms. Prominent Democrats call for Biden to drop out. Supporters debate Harris as a stronger contender. Biden's aides questioned about Harris' ability to win. Biden remains defiant amid dropping support. Inner circle shrinks, leaving Biden cocooned. Uncertainty looms over Biden's political future.