My guess is that they are doing it to sway the uneducated (in terms of US political knowledge) to vote democrat. Imagine you are an immigrant, or a US citizen that's not too familiar with our government, and your thinking might go like so:

USA good -> USA democracy -> democracy therefore good

Now who do I vote for, republican or democrat? Well maybe I'll assume a democrat is for democracy and I have already decided democracy is good therefore I'll vote for the democrat.

My guess is that they are doing it to sway the uneducated (in terms of US political knowledge) to vote democrat. Imagine you are an immigrant and your thinking might go like so:

USA good -> USA democracy -> democracy therefore good

Now who do I vote for, republican or democrat? Well maybe I'll assume a democrat is for democracy and I have already decided democracy is good therefore I'll vote for the democrat.