Dr. John Dee is a broken voting machine?

Can Dr. John use his special text more than once in a referendum?

Dr. John Dee
Clan: Tremere (group 4)
Capacity: 9
Disciplines: ANI AUS DOM THA chi
Camarilla Prince of London: Ventrue in combat with John may not end combat as a strike. During a referendum, John may burn a card that requires Thaumaturgy from your hand to gain two additional votes.

No, he isn't. His cardtext follows clearly the "During X, do Y" paradigm, so he's confined to using his special ability once per referendum.

What Ralf said.

Also:
www.vekn.net/index.php/all-rulings/general-rulings

Terminology:

* "During time period X, (you may) do Y" limits Y to once per phase X. [LSJ 19970625]