You're not trying to convince the straight-ticket Lib Dems to vote for your guy. You're trying to convince the moderate to conservative person to vote for your guy instead of just staying home.
If you don't remember that, you will be reminded in November.
It's an uphill battle, regardless. The 'Rats gerrymandered the lines in NC, and this district was drawn for one of theirs. It would be nice to see 2 Black Republicans heading to Congress from NC in the form of Mr. Robinson and Dr. Ada Fisher, but it's, sadly, unlikely.