... undermine basic notions of fairness that we cherish as Americans, as well as the trust between police and their communities that is so crucial to keeping us safe.”

Obama said he had “instructed members of my administration to closely monitor the situation and examine the civil rights and other implications of this legislation.” That would imply that his administration would be ready to act in any of the expected civil rights suits likely when the law goes into practice.

But the president signaled that the issue is broader, going to the question of who determines border policy, a state or the federal government.

The lead federal agency on border issues is the Department of Homeland Security, headed by Secretary Janet Napolitano, a former Democratic Arizona governor who twice vetoed legislation similar to the bill signed Friday.

The department, does not comment on specific state legislation, but the federal policy has been clear.

The federal government does not want a patchwork of differing state laws on immigration and wants a comprehensive solution.

The federal government has also concentrated its efforts in fighting criminals, strengthening border security, and on fugitives, rather than the undocumented worker who could be seen as the target in the Arizona law.

“DHS continues to focus on smart, effective immigration enforcement that places priority on those dangerous criminal aliens who present the greatest risk to the security of our communities, on employers who continue to drive illegal immigration by knowingly hiring undocumented workers, and by surging law enforcement resources at the Southwest border,” a DHS spokesman said by e-mail.

“If we continue to fail to act at a federal level, we will continue to see misguided efforts opening up around the country,” Obama said, pointing to Arizona. “As a nation, as a people, we can choose a different future -- a future that keeps faith with our history, with our heritage, and with the hope that America has always inspired in the hearts of people all over the world.”

But that requires a political solution, always a problem in an election year, especially now when partisanship has so poisoned the legislative air in Washington.

Democratic House Speaker Nancy Pelosi has said her chamber will not act on an immigration overhaul until the Senate first moves, a recognition of the tough vote. Some Democrats in the House are still smarting at how the healthcare battle played out, with the House having to go out on a limb only to be stuck with a more conservative bill. They would like to avoid a repeat over immigration.

In the Senate, New York Democrat Charles Schumer and Republican Lindsey Graham have been working on a bipartisan bill, but it is unclear whether there is enough time or will to bring it up before the elections.

Immigration reform is unlike financial regulation reform, on which Democrats and Republicans can find some common ground because there is a common enemy, greedy Wall Street bankers and traders. On immigration there is no common enemy to unite those more used to sparring than speaking.

“I’ll continue to consult with Democrats and Republicans in Congress, and I would note that 11 current Republican Senators voted to pass immigration reform four years ago. I’m hopeful that they will join with Democrats in doing so again so we can make the progress the American people deserve,” Obama said.

Of course, one of the leading Republicans who pushed for immigration reform was Arizona Sen. John McCain, Obama’s opponent in the presidential race. McCain faces a tough primary from a candidate even more conservative than he is. McCain has said he supports the Arizona bill.

--Michael Muskal