Just for kicks, I looked up all the presidential elections since I reached the age of majority.
1988 George H. Bush vs Michael S. Dukakis
1992 William J. Clinton vs George H. Bush vs H. Ross Perot
1996 William J. Clinton vs Robert J. Dole vs H. Ross Perot
2000 George W. Bush vs Albert A. Gore vs Ralph Nader
2004 George W. Bush vs John F. Kerry
2008 Barack Obama vs John McCain
2012 Barack Obama vs Mitt Romney
2016 Donald Trump vs Hillary Clinton
In 1988, I believe I voted for the socialist candidate, but don't recall who that was.
1992, I voted for Clinton (in part because of Hillary)
1996, Clinton
2000, Gore
2004, I voted for Nader.
2008, Obama, and I cried when he won because I was so happy. I also played Chocolate City by Parliament (You don't need the bullet when you got the ballot).
2012, Obama, despite my general disappointment with him. Jad Huntsman been the R nominee, I would have considered voting for him.
2016, I wrote in Bernie Sanders.
So, yes, I overwhelmingly, but not completely, have voted for the big D for president. And if I didn't, it's because they weren't far enough left. While I can understand the value of strategic voting, I can't always do it, particularly when I lived in a super red state (Utah) or a very blue state (Oregon) where it doesn't completely matter.
For state and local elections, I am more likely to support 3rd party or independent candidates. For example, I did vote for the aforementioned Huntsman in 2008, for his second term as governor of Utah - which was interrupted when Obama appointed him ambassador to China.