As of the GOP convention--coronating Romney, most likely--the only pro liberty candidate left running for the presidency will likely be GJ. Early money sent now will be matched, then used for Internet and radio ads, as well as fundraisers that bring in more funds.
I'm looking past summer. There are some good LP presidential and vice-presidential candidates. We have this opportunity every four years to make the plug for Constitutionally limited government and ending the various wars--domestic and international.
The LP gets the opportunity every 4 years but it's a very limited opportunity. Just being realistic here, Johnson isn't getting invited to any of the Presidential debates, isn't getting any major press time and he isn't going to have enough money to market his message nationwide. How many people that aren't already libertarian-oriented is Johnson, or any LP candidate going to reach?
Paul has already been down that road and that's why he went to the GOP. And this cycle represents a golden opportunity in the GOP because they delegates going to Tampa may decide the nominee. And the Paul camp will likely have significant leverage in that convention. The more delegates he gets the more leverage he has. And he plans to use that leverage to make a splash on a national level.
Johnson does just haven't that sort of opportunity in front of him, at least not this cycle, not at this time. If the GOP abandons the Paul camp, then there will be a lot of disaffected GOPers. But they haven't given up yet.
IMO, if Johnson has a chance to make a huge impact, it's as the successor to Paul (official or not). But you can't succeed the leader until he's done. And Paul isn't done. He's still building the movement, still working towards the biggest gains he can make.