Leaders in both chambers of Congress have indicated that immigration reform is a legislative priority in the 113 th Congress. The main elements of "comprehensive immigration reform" (CIR) legislation typically include increased border security and immigration enforcement, improved employment eligibility verification, revision of legal immigration, and options to address the millions of unauthorized aliens residing in the country. In January 2013, a bipartisan group of Senators proposed a framework for CIR that would address these issues and include new temporary worker visas. Several of these elements also were among the features that President Barack Obama emphasized later the same month when he called for the 113 th Congress to "quickly" take up CIR legislation, though President Obama has not endorsed new temporary worker visas. Similar to President Obama's recent statements on CIR, former President George W. Bush stated that comprehensive immigration reform was to be a top priority of his second term. President Bush's principles of immigration reform included increased border security and enforcement of immigration laws within the interior of the United States, as well as a major overhaul of temporary worker visas, expansion of permanent legal immigration, and revisions to the process of determining whether foreign workers were needed. Then—as well as now—the thorniest of these issues centered on unauthorized alien residents of the United States. Substantial efforts to enact CIR legislation failed in the 109 th and 110 th Congresses, prompting some to characterize the issue as a "third rail" that is too highly charged to touch. The 2006-2007 CIR bills were sweeping in scope and ranged from just under 500 pages to over 800 pages. The three major bills CIR bills that received floor action were Border Protection, Antiterrorism, and Illegal Immigration Control Act of 2005 ( H.R. 4437 as passed by the House in the 109 th Congress), Comprehensive Immigration Reform Act of 2006 ( S. 2611 as passed by the Senate in the 109 th Congress), and Comprehensive Immigration Reform and for other purposes ( S. 1639 as considered by the Senate in 110 th Congress) This report opens with brief legislative histories of CIR in the 109 th and 110 th Congresses. A comparative overview of key CIR provisions in the three bills that received floor action in the 109 th and 110 th Congresses follows. In addition to a narrative discussion of how the bills addressed the main provisions of CIR, the report provides a table that presents a comparative summary of the key features of the bills. The report concludes with observations contrasting the 2006-2007 period with the context of today's CIR debate. The report also provides an appendix that summarizes the three major CIR bills. The Immigration and Nationality Act (INA), which was first codified in 1952, contained the provisions detailing the requirements for admission (permanent and temporary) of foreign nationals, grounds for exclusion and removal of foreign nationals, document and entry-exit controls for U.S. citizens and foreign nationals, and eligibility rules for naturalization of foreign nationals. Congress has significantly amended the INA several times since 1952, most notably by the Immigration Amendments of 1965, the Refugee Act of 1980, the Immigration Reform and Control Act of 1986, the Immigration Act of 1990, and the Illegal Immigration Reform and Immigrant Responsibility Act of 1996. During the 109 th Congress, both chambers passed major overhauls of immigration law but did not reach agreement on a comprehensive reform package. On November 14, 2005, the Chairman of the House Homeland Security Committee, Representative Peter King, and a bipartisan group of co-sponsors introduced H.R. 4312 , the Border Security and Terrorism Prevention Act of 2005, which was jointly referred to the Armed Services, Homeland Security, and Judiciary Committees. The Homeland Security Committee reported H.R. 4312 on December 6, 2005. That same day, the chairman of the House Judiciary Committee, Representative James Sensenbrenner, introduced the Border Protection, Antiterrorism, and Illegal Immigration Control Act of 2005 ( H.R. 4437 ). On December 13, 2005, the House Judiciary Committee reported H.R. 4437 along a party-line vote. H.R. 4437 included a number of provisions identical to those in H.R. 4312 , as reported by the House Homeland Security Committee. The House Rules Committee met on December 14, 2005, to consider the rule for floor debate on H.R. 4437 and reportedly heard six hours of testimony. In a move that many observers considered a key vote, the Rules Committee rejected a motion to allow an amendment that would have created a guest worker visa program. The amendment, co-sponsored by Arizona Republicans Jim Kolbe and Jeff Flake and California Democrat Howard L. Berman, would have allowed unauthorized aliens to register for new temporary visas. The Rules Committee did agree to 15 amendments that could be offered on the floor and approved the rule for H.R. 4437 early on the morning of December 15, 2005. On December 16, 2005, the House debated and passed H.R. 4437 , as amended. The legislation had provisions on border security; the role of state and local law enforcement in immigration enforcement; employment eligibility verification; and other enforcement-related issues including immigration fraud, worksite enforcement, alien smuggling, and migrant detention. H.R. 4437 also contained provisions on unlawful presence, voluntary departure, and alien removal. The Chairman of the Senate Committee on the Judiciary, Senator Arlen Specter, circulated a draft CIR bill on March 6, 2006 (Chairman's mark) that would have substantially increased legal immigration as well as strengthened border security and immigration enforcement. S. 2454 , the Securing America's Borders Act, which Senate Majority Leader William Frist introduced on March 16, 2006, had border security and employment verification provisions that were similar to H.R. 4437 and had provisions revising and increasing legal immigration that were similar to the Chairman's mark. After three weeks of debate, the Senate Judiciary Committee favorably reported a modified version of the Chairman's mark, which also included provisions for a broad legalization program similar to those originally proposed by Senators Edward Kennedy and John McCain. The Senate failed to invoke cloture on S. 2454 and the Judiciary Chairman's mark during floor debate from March 28, 2006 to April 7, 2006. Senators Chuck Hagel and Mel Martinez proposed alternative language to keep immigration on the Senate's agenda. Chairman Specter, along with Senators Hagel, Martinez, Kennedy, McCain, Lindsey Graham, and Sam Brownback, introduced this compromise as S. 2611 on April 7, 2006, just prior to the April recess. Because this legislation reflected many of the policy features that Senators McCain and Kennedy had articulated over the past few years, S. 2611 became known as the McCain-Kennedy bill. It combined provisions on enforcement and on unlawful presence, voluntary departure, and removal with reform of legal immigration. These proposed revisions to legal immigration included expanded guest worker visas and increased legal permanent admissions. S. 2611 also would have enabled certain groups of unauthorized aliens in the United States to become legal permanent residents (LPRs) if they paid penalty fees and met a set of other requirements. After several days of debate and a series of amendments, the Senate passed S. 2611 , as amended, by a vote of 62-36 on May 25, 2006. Over the summer of 2006, a variety of legislative maneuvers were considered to have both chambers pass an immigration bill with the same number so that a conference committee could be formed on CIR and to overcome other procedural barriers the legislation faced. President George W. Bush reaffirmed his support for CIR. "Congress is now considering legislation on immigration reform; that legislation must be comprehensive," President Bush said. "All elements of the problem must be addressed together, or none of them will be solved at all." Congressional leaders, however, were unsuccessful at forming a conference committee, and House-passed H.R. 4437 and Senate-passed S. 2611 expired with the end of the 109 th Congress. As the 110 th Congress opened, there were widespread reports that Senators Kennedy and McCain were meeting with Representatives Luis Gutierrez and Jeff Flake to discuss a bipartisan approach to CIR and were instructing their staffs to draw up a discussion draft based on S. 2611 . On May 9, 2012, Senate Majority Leader Harry Reid introduced S. 1348 , the Comprehensive Immigration Reform Act of 2007. As introduced, S. 1348 was virtually identical to S. 2611 , which the Senate had passed in the 109 th Congress. Republican support for S. 1348 , however, was lacking in the 110 th Congress. According to Roll C all, "(A)ll 23 Republicans who voted for last year's immigration bill sent a letter to Majority Leader Reid on Wednesday warning they would not vote for that measure again and calling on the Majority Leader to allow more time to work out a bipartisan deal." Senators Kennedy and Specter introduced a bipartisan compromise proposal for comprehensive immigration reform on May 21, 2007, as S.Amdt. 1150 , as the floor debate on S. 1348 began. Similar to S. 1348 (and its predecessor S. 2611 ), the bipartisan compromise included provisions aimed at strengthening employment eligibility verification and interior immigration enforcement, as well as increasing border security. This substitute language differed from S. 1348 in several key areas of legal immigration. It would have substantially revised legal immigration and temporary worker programs with provisions that differed from S. 1348 . Unauthorized aliens in the United States would have been able to become LPRs if they met certain requirements and paid penalty fees in a re-worked legalization process. The Senate failed to invoke cloture on this version of CIR on June 7, 2007, after supporters and opponents of the bill could not agree on a number of amendments to be considered. Senate Majority Leader Reid and Senate Minority Leader Mitch McConnell publicly affirmed their commitment to debate comprehensive immigration reform in June 2007.