The U.S. Department of Justice is filing a lawsuit against the state of Arizona for its controversial anti-immigration law, which President Obama has publicly criticized as counterproductive and which is scheduled to go into effect later this month. The possibility of a federal challenge of the law has been discussed for weeks, and it appears that the Obama administration is now following through. Here's what to expect.

• The Federal Govt's Legal Argument The Washington Post's Jerry Markon writes, "The lawsuit, which three sources said could be filed as early as Tuesday, will invoke for its main argument the legal doctrine of 'preemption,' which is based on the Constitution's supremacy clause and says that federal law trumps state statutes. Justice Department officials believe that enforcing immigration laws is a federal responsibility, the sources said. But the filing is likely to have a civil rights component as well, arguing that the Arizona law would lead to police harassment of U.S. citizens and foreigners."

• All About Federal vs. State Authority The Associated Press' Bob Christie writes, "The lawsuit will argue that Arizona's new measure requiring state and local police to question and possibly arrest illegal immigrants during the enforcement of other laws, like traffic stops, usurps federal authority." This suit is "setting the stage for a clash between the federal government and state over the nation's toughest immigration crackdown."

• Could Provide Much-Needed Boost for Obama, Reid The Washington Post's Greg Sargent suspects political motivation. "The White House is reported to be worried that Obama's dip in popularity among Latinos will adversely impact the 2010 and 2012 elections. Harry Reid also needs big Latino support to win reelection. ... a major, high-profile lawsuit like this one could do nearly as much as a legislative push on the issue to excite Latino and other Dem base voters, at least in the short term. It could restart the national argument over immigration, push the issue to the forefront again, and demonstrate the Obama administration's willingness to use the power of the Federal government to defend Latinos' civil rights."

• Presents Tough Choice for GOP   Hotline's Reid Wilson explains, "The challenge will have serious political ramifications -- both positive and negative -- for each party. Expect AZ Gov. Jan Brewer (R) to jump all over the Feds, and for fellow GOPers to follow suit. ... But watch out, GOPers: Hispanic voters are already wary of your party, and too much harsh rhetoric on SB 1070 will push them more into the Dem fold."

• Arizona Republicans Condemn Suit The Hill's Eric Zimmerman reports, "Sens. John McCain (R-Ariz.) and Jon Kyl (R-Ariz.) criticized the Justice Department on Tuesday for reportedly planning a lawsuit to overturn the Arizona immigration law." McCain and Kyl say that the federal government failed in its responsibility to properly implement and enforce immigration barriers and thus has no standing to enforce federal preemption of state immigration policies.

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