Explanation:

- A major advertising _election_ was planned to launch the new brand of garments.

- An election is related to the process of voting to choose leaders, not relevant for advertising.

- A major advertising _pension_ was planned to launch the new brand of garments.

- Pension refers to a regular payment made during retirement, unrelated to advertising.

- A major advertising _campaign_ was planned to launch the new brand of garments.

- ? A campaign refers to an organized effort to promote a product, which fits perfectly with launching a new brand.

- A major advertising _ambush_ was planned to launch the new brand of garments.

- Ambush generally means a surprise attack, not fitting for launching a brand.