What could be inferred from the opinions themselves, and was suggested by some contemporaneous reporting (including Paul’s), has been confirmed by Joan Biskupic:
Biskupic reports in detail for the first time on the machinations of the Obamacare case, revealing that Roberts started out in a different place. She writes that he initially voted with the four other conservatives to strike down the ACA, on the grounds that it went beyond Congress’s power to regulate interstate commerce. Likewise, he initially voted to uphold the ACA’s expansion of Medicaid. But Roberts, who kept the opinion for himself to write, soon developed second thoughts.
Biskupic, who interviewed many of the justices for this book, including her subject, writes that Roberts said he felt “torn between his heart and his head.” He harbored strong views on the limitations of congressional power, but hesitated to interject the Court into the ongoing health-insurance crisis. After trying unsuccessfully to find a middle way with Kennedy, who was “unusually firm” and even “put off” by the courtship, Roberts turned to the Court’s two moderate liberals, Stephen Breyer and Elena Kagan. The threesome negotiated a compromise decision that upheld the ACA’s individual mandate under Congress’s taxing power, while striking down the Medicaid expansion. Future scholars will endlessly probe this fascinating moment in judicial history, but Biskupic deserves credit for writing the first draft.
The fact that Roberts initially voted to uphold the Medicaid expansion makes makes me a touch less sanguine about Kagan and Breyer’s strategic voting than I was at the time, but (especially given Roberts’s volatilty) preserving the ACA’s industry regulations and still getting most of the country the Medicaid expansion was still probably a deal worth making. Nor is it terribly surprising that the argument for re-writing or striking down the Medicaid expansion — which had a stronger case for constitutionality than the de facto national drinking age the Court upheld in Dole — was such a dog even Roberts (let alone Breyer and Kagan) didn’t initially buy it.