A lot of people I know, myself included, who voted Ron Paul in the Republican primary in Wisconsin or caucused Ron Paul in Minnesota will be voting Gary Johnson this November.
Voting Johnson makes more sense than writing in Ron Paul since those votes will be grouped into "other - write-ins" and wont have much significance going forward.
A big turnout for Johnson makes a much better statement and could attract a lot of attention.
Want DP delivered to your inbox daily? Subscribe here: