An advertiser wants flexible spending each day with the ability to increase spend on particular days leading up to the holidays for better performance. How should the advertiser set up its campaign?

Campaign Budget Optimization (CBO) is the correct choice because it allows Pinterest to automatically distribute the campaign's budget across ad groups to achieve the best results. This flexibility is ideal for increasing spend on specific days leading up to holidays, as the system will allocate more budget to ad groups performing well during those peak times. Leveraging new campaigns for key dates would be less efficient and harder to manage. Average daily budget provides less flexibility than CBO for optimizing across ad groups. Lifetime budget sets a fixed total amount for the entire campaign duration, which doesn't allow for dynamic daily adjustments based on performance or holiday surges.