Yes, there is this. But there is also the fact that he’s been raising alarms on ACORN and the Obama campaign has not responded to his campaign’s communications on the matter:

A collection of letters via the McCain campaign:

Sen. John McCain’s letter to Rep. John Conyers, Chairman of the Judiciary Committee
Sens. John Danforth and Warren Rudman’s letter to Rep. Conyers
Sens. Danforth and Rudman’s letter to Obama Campaign Manager David Plouffe
Sens. Danforth and Rudman’s letter to DNC Chairman Howard Dean

We can all — Republicans and Democrats — be against voter fraud … right?