What Supreme Court decision will have most political impact? Not health care

Washington may be in a state of frenzied anticipation over the upcoming US Supreme Court decision on President Obama's health-care reform. But the judicial ruling that could have the bigger impact on the presidential election may have already happened.

We're referring to the court's decision on the Arizona immigration law, which came Monday morning and served as a kind of capstone to an eventful week and a half dominated largely by the politics of immigration – a period that was actually pretty good for the president (health-care predictions notwithstanding) and pretty uncomfortable for Mitt Romney. 

Let's review. Over the past 10 days:

• Mr. Obama unexpectedly moved to allow young undocumented immigrants who were brought to the United States as children to remain in the country to work and study – in effect, instituting a policy similar to the DREAM Act, which had stalled in Congress. (Obama's version, however, does not include a path to citizenship.) Mr. Romney, who had vowed during the primary campaign to veto the DREAM Act, would not say whether he would overturn Obama's decision as president.
• ABC News broke a story saying that Florida Sen. Marco Rubio – one of the GOP's most prominent Hispanic officeholders and a frequently mentioned vice-presidential contender – was not even being vetted by the Romney campaign. Romney allowed the story to percolate for nearly a full day before coming out and telling reporters "of course" Senator Rubio was being vetted.
• Obama and Romney both gave speeches at the National Association of Latino Elected and Appointed Officials, where they exchanged biting barbs – Romney reminding the audience that Obama had failed to tackle immigration reform; Obama reminding them that Romney had promised to veto the DREAM Act. Obama received an enthusiastic response, while Romney's reception was widely characterized as "polite."
• And then on Monday, the Supreme Court issued a decision throwing out most of the Arizona immigration law – while upholding its controversial "show me your papers" element, requiring police officers to check the immigration status of those they stop or detain if the officers have reason to believe they are in the country illegally. Romney, who had called the Arizona law "a model" during the campaign, issued a statement criticizing the president for failing to lead on immigration reform, but notably avoiding taking a position on the court's ruling. Later, he told supporters at a fundraiser that he wished the court would give states "more latitude" to enforce immigration laws. Obama directly praised the court's decision but said he was "concerned" about the provision it upheld, saying "no American should ever live under a cloud of suspicion just because of what they look like."

Polls have shown that most independent voters approve of the Arizona law (as well as a strong majority of Republicans), so it's possible Romney will win some supporters for his stance. But it seems more likely that the decision will galvanize Hispanics, who were strongly opposed to the law. 

And if that's the case, we may be about to see Obama's lead among Hispanic voters go from "strong" to "utterly devastating." 

According to a USA Today/Gallup poll released Monday – but conducted before any of the above events – the president was leading Romney among Hispanics by 66 to 25 percent. That puts Obama almost exactly where he was in 2008, when he won 67 percent of the Hispanic vote. But given all that has recently unfolded – and that a Gallup survey conducted last week found 8 out of 10 Hispanics approve of Obama's move to protect children of illegal immigrants from deportation – it's entirely possible Obama's lead in the polls will widen.

Notably, the USA Today/Gallup poll found Romney running six points behind Sen. John McCain's 2008 performance (Senator McCain won 31 percent of Hispanics). If the 6 percent who supported McCain but are not currently backing Romney wind up choosing Obama instead, that would put the president above 70 percent among Hispanics.

More important, it could shift the electoral map – making Western states like Nevada, New Mexico, and Colorado far tougher climbs for Romney and making Arizona a genuine tossup. If the West starts to shift strongly toward Obama, that leaves Romney with a much, much narrower path to the White House.