Andrew Gillum is considered to be a progressive Democrat. This means that he feels that the reform of the United States in a more democratic manner will surely change the country as a whole. He has shown that he advocates programs that are related to the democratic party.
Aside from being a part of the democratic party, he is also an advocate of democracy. There is something about democracy that he genuinely believes in. Americans who are also Democrats have a higher chance of voting for him just in case. He may not have some of the qualifications that other candidates have but his party may boost his ratings.