The Prime Minister's good luck message to Andy Murray ahead of his quarter-final tie sparked concern among fans who fear the "curse of Cameron".
On previous occasions, sporting stars have seen their hopes of glory fade following a message of support from the Tory leader.
Bookmaker William Hill has launched a campaign to "BanCam" from issuing messages of encouragement.
A spokesman said: "A message of luck from David Cameron to British sports stars is like kryptonite to Superman. We are imploring the Prime Minister to instead send his messages to their opponents."
Andy Murray has become the first British tennis player to win the men's singles title at Wimbledon for 77 years.
If you can't face the queues for Murray Mound at Wimbledon, several outdoor big screens in London are showing the men's final for free.
Germany's Sabine Lisicki is set to play France's Marion Bartoli in the women's Wimbledon final today.