Harris is positioning herself as the candidate who will unite the nation in opposition to Trump's divisive rhetoric. This speech didn't just address the Democratic Party but reached out to people who may not usually be inclined to vote for Harris but who are looking for an alternative to Trump. Harris did a great job of relating to voters by telling her backstory while also providing her vision for a brighter future.
Harris isn't fooling anyone by selling herself as the "unity candidate" even as she almost threatens undecided voters to pick her approach only. She may have toned down her rhetoric about Trump in this speech, but her past accusations about him — not to mention Biden's hateful comments about Trump's supporters — make it clear she's not selling joy or a brighter future, just more of the misery of the current administration.