The NYT has more here.
"Political campaigns don’t have an off-season, but the brief lull between last November’s general election and now has given us time to make some updates to our Campaign Finance API. This round of changes focuses on additions to committee and filing responses, with particular emphasis on customizable collections of electronic filings and PAC contributions to candidates. We’ve also added support for JSONP requests. And in saying hello to the 2012 election cycle, we’re saying goodbye to Version 2 of the API, so all users should now be using Version 3."