All Candidate Limit

I was just checking my E-Mail and in my in-box was one from the Club for Growth. I usually get a chuckle out of reading them, and this one was no exception. It did contain one thing that has me puzzled. From the Club For Growth:

Arizona Senator Jon Kyl earned the #1 ranking in the Club for Growth rating of the Senate and has taken a key leadership role time after time. Now he is being challenged by a former Democratic Party state chairman, a limousine liberal developer who has poured over $10 million into his campaign.

He triggered the "millionaire's amendment" in the election laws, so you can now donate up to $6,300 to Jon's campaign, and only $2,100 counts against your $40,000 all-candidate limit.

$40,000 all-candidate limit? I, in all my life have never heard of such a thing. Does anybody out there have any information about this?