Aside from Polls, another useful tool to gauge voter interest in candidates is by observing online search trends. The below Google Trends chart (snapshot from today) shows the online search trends for 2019 for the Top 5 Democratic candidates running for President in 2020.

Source: Google Trends (trends.google.com/...)

As you can see each candidate receives an initial trend boost following their official announcement of their candidacy for President in 2020. Joe Biden received an early trend bump 2 weeks prior to his announcement when multiple allegations of inappropriate touch surfaced. Kamala Harris and Bernie Sanders are currently in the lead and tied with 23% of the Top 5 Democratic candidate Google Searches.

Google Trends top 5 candidates Online Interest Kamala Harris 23% Bernie Sanders 23% Joe Biden 19% Pete Buttigieg 12% Elizabeth Warren 10%