The Vice President is an extremely electric person and a dynamic leader, so it's no surprise her popularity is on the rise. She has the type of ideas that will move the US forward. An excited Democratic voter base is uniting around Harris at the same time Republicans and the Trump campaign are trying to distance themselves from Project 2025, which is the basis for most of their platform.
Harris should enjoy her honeymoon with voters while it lasts. Soon enough the electorate will come to terms with how closely aligned Harris is with Biden's failed policies and how dangerously liberal her record was prior to becoming the vice president. The fundamentals of this election haven't changed much since the Democrats' change in candidate, and Trump is still in pole position.