There are things you can do to persuade me to support your candidate in the upcoming primaries, and there are things you can do that will make it less likely that I will support him or her.
I'll start with the things I find most persuasive.
1. Tell me where your candidate wants to take the country: what Bush senior called "the vision thing." What kind of America do they want to make? What challenges do they see facing the country in the coming years, and how do they propose to meet those challenges? What will their priority list look like if they win the presidency?
Tell me with whom your candidate stands. "Who" is more important to me than "what" s/he stands for, because successful politics, in a democracy, is about building the biggest coalition. I remember 30 years ago, a sports reporter asked Terry Bradshaw what strategy he would deploy to win the Super Bowl. His response? "We're going to try and out-score the other team." Well, exactly. The Democratic nominee's only job is to Get more people to vote for our guy than the Republicans can get to vote for theirs.
Tell me how your candidate will help the people named in point two. Specific policy proposals are best here. Just saying your candidate will help working class folks because he or she has gotten an endorsement from this or that union is that old logic fallacy, begging the question. Give me specifics: Is he or she for card check legislation? A living wage? What concrete porposal have they made about univesal health care?
What skills does your candidate have in terms of getting citizens on board with an agenda? How persuasive is s/he? Has he or she demonstrated an ability to galvanize people, get them supporting his/her agenda? Are they raising lots of small donor dollars? Are large crowds coming to his/her events?