Actually, I believe you really can not influence anything by voting. A single vote will not influence anything if the voting population exeeds a certain limit. Still you can postulate a moral resposibility to vote.
Often it is said that if nobody did vote, democracy would break down. This is stupid. It annoys me every time I have to read it. You have to take soziology into account here. Somebody who thinks about not voting belongs to a small minority of people willing to think about their voting behaviour. The majority of people does not think about voting in such a way and never will. Either they are uninterested or they are firm in their opinion to vote.
However, you can influence the outcome of a election by influencing other people. If you propagate the ideas of your party, even among your friends, you could theoretically start a snowball like prozess, that influences enough people to make adifference. It is highly unlikely, but it is somethin everybody can do without becoming a politican.
So I say, a little help for your party is what you should do if you feel a responsibility to democracy.