On October 21, the Indiana Democratic Party issued a press release, detailing problems with John McCain’s petition to be on the Indiana presidential primary ballot in 2008. See it here. Although the release has many criticisms of the petition, the release does not allege that any signatures were forged. Indiana Democrats did this study partly to counter the publicity that the 2008 Democratic presidential primary petitions for Barack Obama and Hillary Clinton both contained some forgeries, enough so that if the forgeries had been detected, neither would qualified. Indiana requires 500 signatures from each of the nine U.S. House districts.
In 2008, the only candidates who appeared on the Republican presidential primary ballot in Indiana were John McCain, Mike Huckabee, Ron Paul, and Mitt Romney. Obama and Clinton were the only Democrats who qualified.
The saddest part of the Democratic press release is at the bottom, where the party suggests improvements in the Indiana ballot access law for presidential primaries. Nothing is said about simply eliminating petitioning. Most states have eliminated mandatory petitions for candidates seeking a place on a presidential primary ballot, at least for candidates who are discussed in major media or who have qualified for primary season matching funds. Thanks to Rick Hasen for the link.