Definitely take a look at this post by Professor Cohen on the Voting Paradox in McDonald v. Chicago.

Before McDonald, it was basic blackletter constitutional law that the incorporated rights from the Bill of Rights were incorporated through the Due Process Clause. Although some scholars and jurists supported incorporating the Bill of Rights through the Privileges or Immunities Clause, the Supreme Court had squarely rejected that approach and had limited that clause to have a very narrow effect. Nonetheless, the lawyers challenging Chicago’s handgun ban included the Privileges or Immunities Clause argument in their briefing, making it their primary argument before the Supreme Court. The decision was questioned by some, as the lawyers virtually ignored the Due Process Clause argument that was grounded in the currently-existing law about incorporation and instead focused on an argument that no one could possibly imagine getting a majority of the Court.

I’ll quibble with one element of this argument, as the Petitioners did not “ignore” the due process argument, though they spent very little time on it in their briefs.
Cohen also provides an interesting example of how the votes could have resolved in Gonzales v. Carhart if the Doctors had also briefed a Commerce Clause argument:

Without changing the Justices’ opinions on the due process issue, the lawyers for the doctors could have won their case and convinced the Court to strike down the federal law by introducing a second argument — that the federal law went beyond Congress’ enumerated powers under the Commerce Clause. Although the Court has only struck down two laws since 1937 as going beyond Congress’ powers under this clause and there was no real argument that the federal abortion law was like those two laws, at least one Justice probably would have found that the federal law was not authorized by the Commerce Clause. Justice Thomas has written extensively about limits on Congress’ powers under the Commerce Clause, going so far as writing that “wholly intra state, point-of-sale transactions” are not within Congress’ authority and that “health laws of every description” are beyond Congress’ authority as well. If he had remained faithful to these previous pronouncements, he would have voted to strike down the federal law under the Commerce Clause even though he believed it was constitutional under the Due Process Clause. That he wrote a concurrence in Carhart specifically explaining that he was not reaching the Commerce Clause issue because it was not raised by the parties drives this point home.

Definitely worth a read.