The rule was not last-minute, it was done in October, 2 months before the signatures were due.
And of course, having a rule that makes it easier to get on the ballot would hardly “disenfranchise voters”. What argument are we discussing, that it was too easy for Romney because he got 15,000 signatures, or too hard for Gingrich because his signatures were checked? The 15,000 signature “rule” was a time-saving measure for the RPV, and didn’t in any way make it harder to get on the ballot. In the absense of that rule, every candidate would have all the signatures checked, and Gingrich and Perry would still be out.
I have no doubt that a review of Romney’s signatures would find 10,000 valid ones.
Doesn’t matter, the rule was done in the middle of the process when they were already supposed to be collecting signatures. That gives an unfair advantage to people who may have been further along in the signature collection process. Some may have postponed doing it, believing they’d only need 10,000.
As I understand it, the signatures were NEVER checked before. The check against addresses was instituted in October for those submitting less than 15,000. That made it harder for anyone to avoid the check. Before that you only needed 10,000 and there was no check.