Why Sarah Silverman could be the Democrats' secret weapon

Every family needs a sibling to keep the house in order when chaos breaks out. It's usually the middle sibling who can see both sides of the argument.

Right now, the Democratic Party needs a middle child – a sibling who is not a part of the fight but can see both sides – to bring the party together.

That party broker is not Bernie Sanders. He is too identified with the fight. When his supporters hear him speak, they will only be reminded of why they believe the party cheated them out of a win. Yes, Sanders must continually show support for the nominee Hillary Clinton as he has done, but he can't remain the focal point.

Instead, comedian Sarah Silverman, who actively supported Sanders during the primary, can bridge the gap. She is the poster girl who exemplifies the empathy that Sanders' supporters feel. She also actively campaigned for Sanders and shares many of his platform beliefs, so she has the credibility needed to sway Sanders' supporters.

She tried last night to bring the party together, but hit some bumps and resorted to insults. Instead of belittling Sanders supporters by calling them 'ridiculous' for not supporting Clinton, she could have appealed to their common interests: higher minimum wage, Supreme Court appointments, climate change and women's health issues.

Even so, Silverman makes for a great brand ambassador because she is not associated with politics. She's participating in the political process because she wants to make the party better, similar to what Sanders followers want.

The party can utilize her appeal to millennials and Sanders supporters for the rest of the week by letting her mingle with his die-hard delegates, selling them privately on why Clinton is the best option for unifying the party.

After the convention, however, the message must focus on Clinton and her running mate Tim Kaine. Sanders and Silverman can be used sparingly, when the campaign is speaking to more progressive crowds.

But, they should not be placed in high profile speaking engagements, especially in swing states. Starting next week, the Clinton/Kaine campaign needs to start bringing moderates, independents and undecided voters back to the table.

The more Sanders and Silverman distract from that message, the more the party stays divided. And only one person benefits from that: Trump.

In the end, voters – regardless of party – look for optimism and hope. If Clinton can inspire moderate and independent voters with a hopeful future, she might be able to win even without the "Bernie or Bust" contingent.

Commentary by Mark Macias, head of Macias PR, a global public-relations firm, that has run media and branding campaigns for politicians, tech start-ups, financial firms, nonprofits and companies. He's also author of the book, "Beat the Press: Your Guide to Managing the Media." Follow him on Twitter @markmacias.

For more insight from CNBC contributors, follow @CNBCopinion on Twitter.

More From CNBC

• Top News and Analysis
  

• Latest News Video
  

• Personal Finance