I like some libertarian ideas and read a fair amount of what reason.com and cato.org put on their webpages, but I don't really think that "libertarianism" or libertarians as a voting bloc count for much in this country. Some of their ideas crop up from time to time and get mainstream but it's hard for me to give Cato or the Libertarian Party any credit for gay marriage or weed legalization. What happened with both those issues is that people who cared deeply about them worked really hard for a really long time to make some change. The libertarian websites have recently been crowing about how that means libertarianism is catching on but I just don't see it, and I don't see that the Libertarian Party had a lot to do with moving the needle on those issues.
It could be that libertarian-leaning commentators and writers have helped change some minds here and there. But overwhelmingly for gay marriage in particular it has been gay people and their straight allies getting organized, raising money, and working really hard to change minds since the 90s. I would be willing to bet that if you took 10,000 activists who have been involved in gay marriage (i.e., giving money, handing out flyers, campaigning) well over 50% would registered Democrats, a good chunk would be independent w/strong Dem lean, a very small percentage would registered Republicans, and almost none would be card-carrying Libertarian party members.