The long-awaited health care ruling didn't arrive this morning, but there was another significant announcement: The Supreme Court ruled 5-3 against three components of the controversial Arizona immigration law, while upholding the provision requiring police to check the immigration status of individuals suspected to be in the United States illegally. Whatever the legal or policy merits of the decision—and TNR’s writers and analysts have a take on both matters—the decision places Romney in a difficult spot on immigration issues for the second time this month.

Even though the law has stirred considerable controversy, most polls show that the Arizona law is broadly popular. According to a recent Pew Research survey, 58 percent of Americans approve of the law, including 69 percent of white voters and 84 percent of Republicans. Given broad public and Republican support, Romney has no choice but to endorse the surviving provisions of the Arizona law, should he choose to weigh in. Of course, Latinos are overwhelmingly opposed, with just 21 percent of Hispanics approving and 75 percent disapproving. Significantly, more Latino voters disapprove of the Arizona law than voted for Obama in 2008, suggesting additional downside risks to Republicans and placing Romney in a difficult position.

During the GOP primary, Romney said that Arizona’s immigration laws were a model for the nation (although his comments were largely in the context of other elements of Arizona’s immigration laws, including e-verify, as his campaign has been keen to observe). By returning attention to the Arizona law, the court’s ruling ensures that Romney’s prior comments receive renewed attention. Democrats will focus on reviving Romney’s past comments, and with the Supreme Court poised to hold off on the ACA ruling until Thursday, there is a window when the press will again focus on immigration issues.

If past is prologue, Romney will attempt to skirt the issue—perhaps by simply observing the importance of border enforcement. Sustained attention will make it difficult for Romney to avoid more direct comments, perhaps especially since Romney is fundraising in Arizona right now. Even if Romney avoids weighing in, Democrats will employ Romney’s “model for the nation” comment to such an extent that an explicit Romney endorsement is unnecessary for them to achieve their political objectives.

Few voters are likely to cast their ballots exclusively on the intricacies of immigration policy, but Romney risks further alienating moderate Latino voters who consider the law hostile to the Latino community. Obama stands to benefit to the extent that the DREAM gambit and today’s ruling combine to reinforce that perception among undecided Latino voters who likely supported McCain in 2008. At the same time, the ruling blunts the recurring theme that Obama has not made progress on immigration. The Justice Department’s lawsuit did not produce their preferred outcome, but Obama can take credit for invalidating three provisions of the state’s law.

One should not expect clear and substantial movement toward Obama in the polls, since Obama has already consolidated most of the Obama ’08 Latino vote. As a result, further gains won't be easy. However, most polls suggest that there are more undecided Latino voters than other racial/ethnic groups, and Romney is generally polling below McCain’s final standing. If Obama won an outsized share of undecided Latino voters, he could perform better among Latinos than he did in 2008, even if that seems unlikely given the economic circumstances. It is possible for Romney to overcome a 2008-esque defeat among Latino voters, but he can’t afford further losses. Since immigration represents Romney’s biggest vulnerability among Latino voters, every day that the news focuses on immigration is a bad day for Romney and good day for the President.