Before the Supreme Court decided McConnell, the Fourth Circuit decided North Carolina Right to Life v. Leake. Among other things, the Court struck down North Carolina’s law limiting individual contributions to indepdendent expenditure commitees—the parallel constitutional issue to the 527 issue I’ve been chronicling. The state has petitioned for cert (see here; response time has been extended to March 23).
Here is the Fourth Circuit’s analysis of the issue:

While the Supreme Court has not addressed the constitutionality of limits on contributions to IEPACs, the Court has considered the constitutionality of limits on contributions to political action committees that contribute to candidates. California Med. Ass’n v. FEC, 453 U.S. 182, 69 L. Ed. 2d 567, 101 S. Ct. 2712 (1981) (“Cal-Med”). In Cal-Med, the Court upheld a limitation on contributions to multi-candidate political committees, which by definition make contributions directly to candidates. Justice Blackmun in his concurrence stressed, however, that a different result would follow if a contribution limit “were applied to contributions to a political committee established for the purpose of making independent expenditures.” Id. at 203. Justice Blackmun further explained that multi-candidate political committees are “essentially conduits for contributions to candidates, and as such they pose a perceived threat of actual or potential corruption. In contrast, contributions to a committee that makes only independent expenditures pose no such threat.” Id.
The State argues that it proffered sufficient evidence to demonstrate the corruptive danger posed by independent expenditures and therefore the need to limit contributions to IEPACs. ‘The quantum of empirical evidence needed to satisfy heightened judicial scrutiny of legislative judgments will vary up or down with the novelty and plausibility of the justification raised.” Shrink Missouri, 528 U.S. at 391. If NCRL’s challenge was to the limitation on contributions made to a candidate, either directly or through a political committee, the evidence presented by the State would be sufficient. However, because the corruptive influence of contributions for independent expenditures is more novel and implausible than that posed by contributions to candidates, convincing evidence of corruption is required. Colorado Republican, 518 U.S. at 618. The State, however, failed to proffer sufficiently convincing evidence which demonstrates that there is a danger of corruption due to the presence of unchecked contributions to IEPACs. We agree with the district court that the $ 4,000.00 limitation on contributions to IEPACS is substantially overbroad and unconstitutional.

Granting cert soon on this issue would be one way to resolve the question in time for this election season. Not that the Court is likely to do so.
UPDATE: Marty Lederman points out to me that North Carolina has asked for a grant, remand and vacate in light of McConnell, making any resolution of this issue through this case quite unlikely.
As I think about it, perhaps the following is a more plausible resolution: someone challenges an FEC advisory opinion (or perhaps rulemaking, though that likely won’t be done before May) on 527s in court and seeks expedited review in a district court, and then, depending upon what happens and potential further appeals on an expedited basis, the losing party seeks to get the Supreme Court involved.