Looking at the three candidates’ published lists of supporters, I count the following (possible) duplicates:

At least 30 on Hughes’ list twice:
Mohammed Hanif Asmal, Jan Clein, John Coyne, Brian Ellis, Joan Garrity, John Halliday, Lesley Hardy, Matthew Harris, EP Helme, Jon Hunt, Lawrence Hurt,Altaf Khan, Richard Knasel, Jonathan Lees, Isobel McCall, George Molyneux, Mark Pursey, Jan Revell, Paul Revell, Debbie Roberts, Paul Robinson, Jennifer Sefton, Max Smith, Tim Smith, Marilyn Sumner, Nick Sumner, Tim Symonds, Matthew Thomas, Joy Vincent, Michael Williams; (and a couple more possibles, eg “Powell Mrs E R” / “Nellie Powell”; “J (Mrs) Fisher” / “Jan Fisher”; but there is no reason to doubt the note on the site that there are two different supporters called Norman Fraser, Andrew Morris, David Rendel, MArtin Roberts and Derek Williams.)

3 on Campbell’s list twice:
Colin Hall, Graham Watson, and Sheila Clarke (none of these are uncommon names; possibly there is an elected official and a non-elected member of the same name; also note of two different supporters both named Sarah Green)

6 on both Campbell and Huhne’s lists:
Alan Dean, Pambos Economides, Brenda Smith, John Stevens, David Thomas, Peter Wilson

2 on both Huhne and Hughes’ lists:
Christopher Thomas, David Walker

2 on both Campbell and Hughes’ lists:
Jock Gallagher, Ricardo Sajor