Story highlights Branding experts say Trump's campaign is burdened with a leader whose personal image is suffering

Consumers give Trump lower scores for being distinctive, fun, trendy and stylish, they say

David Sable is CEO of Young & Rubicam. Will Johnson is president of BAV Consulting. Owned by Young & Rubicam Group, BAV studies brand equity. The opinions expressed in this commentary are theirs.

(CNN) Reeling from allegations of sexual assault and falling poll numbers, Donald Trump insists that his "movement powered by millions of people" remains strong. Diehards will stick with the GOP presidential candidate to the end, but his campaign is no juggernaut.

It is instead a sputtering machine burdened with a leader who is becoming the one thing Trump never was before -- boring.

Our company, Young & Rubicam, has studied Trump's consumer brand for many years through surveys and other market research, and our most recent results are eye-opening. In our surveys ending September 30, Trump experiences sharp declines, compared with just three months earlier, in the scores relating to whether people are excited by a celebrity, leader or consumer brand.

Because he has sought to appeal to voters mainly as an unconventional choice, Trump has depended far more on personality than gravitas to sell himself. But it is becoming clear that the public is no longer intrigued by him. Consider the following scores:

-- Consumers who say Trump is distinctive -- down 10%

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