To ensure a diverse mix of influencers in the shortlisting process for a marketing campaign, you might want to consider the following steps:

1. Define diversity: Identify what diversity looks like for your brand. This could extend beyond race and gender to include factors like geographic location, language, fields of interest or even platform preferences.

2. Research: Use influencer marketing platforms, for instance, Flinque to identify and evaluate potential collaborators. These platforms often provide audience insights which define the demographic data of an influencer’s audience.

3. Broaden your criteria: Look beyond follower count and engagement rate. Consider an influencer’s content quality, authenticity, and alignment with your brand’s values.

4. Use metrics effectively: Analyze audience data of potential influencers. Tools offered by Flinque let brands understand the demographic makeup of an influencer’s audience, which can help maintaining diversity.

5. Collaborate with diverse influencers: Strive to include micro-influencers and niche experts, which may help reach different audience segments and ensure a diverse campaign.

Tools like Flinque can be very effective here, as they provide a vast amount of data and analytics that can help brands diversify their influencer portfolio. The suitability of any platform indeed depends on the brand’s specific needs and objectives for their campaign. Always, it’s best to carry out thorough research and planning to ensure your shortlisted influencers add diversity and value to your marketing campaign.