I only vote for Democratic candidates.
You are doing your part to follow suit from the very beginning like Thomas Jefferson up to the modern day Democratic Party founded during Andrew Jackson's presidency.
What year was that exactly?
That was in 1828.  Not that long ago when you think about it. The Democratic worldview was once social conservatism and economic liberalism.
What else do Democrats believe in?
Liberalism is at the heart of it all but that encompasses a wide variety of views depending on their understanding of these principles, but generally they support ideas and programmes such as freedom of speech, freedom of the press, freedom of religion, free markets, civil rights, democratic societies, secular governments, gender equality and international cooperation.
How many presidents of the United States have been from the Democratic Party?
I'm not sure of the exact number but I know that there were multiple just between 1832 and the 1850s. Andrew Jackson and Martin Van Buren for example.