Paul: Do "whatever it takes" to secure the border, end right to citizenship of U.S.-born children of illegal immigrants, no social services for illegal immigrants, aggressive deportation.
Perry: Opposes complete U.S.-Mexico border fence, which he calls "idiocy," instead wants more border agents. Supports continued U.S. citizenship for U.S.-born children of illegal immigrants.
Romney: Would veto legislation that seeks to award legal status to some young illegal immigrants who attend college or serve in the armed forces. Favors complete U.S.-Mexico border fence, opposes education benefits to illegal immigrants.
Santorum: Supports complete border fence, opposes education benefits to illegal immigrants.
Gingrich: Give younger workers the option of diverting Social Security taxes to private retirement accounts.
Paul: Says younger workers should be able to opt out of Social Security taxes and retirement benefits; benefits for today's retirees should be protected.
Perry: Proposes gradually raising retirement age and restricting increases for the wealthy. Previously branded Social Security a "disease," now says it should be saved. Supports private accounts.
Romney: Starting with workers now under 55, raise age to qualify for full benefits, and limit inflation increases for wealthier beneficiaries. Protect status quo for people 55 and older.
Santorum: Proposes immediate steps to lower benefits for wealthier retirees, raise the age to qualify for full benefits and restrict inflation increases in benefits, both for current and future retirees. Supports option of private retirement accounts.
All support eliminating the estate tax and keeping Bush-era tax cuts.
Gingrich: Choice of filing under current system or paying a 15 percent tax, preserving mortgage interest and charitable deductions. Cut corporate tax to 12.5 percent.
Paul: Eliminate the federal income tax and the IRS, and defund close to half the government.
Perry: Choice between current system and 20 percent tax on income, preserving mortgage interest and charitable deductions. For each individual or dependent, exempt $12,500 in income.
Romney: No one with adjusted gross income under $200,000 should be taxed on interest, dividends or capital gains. Cut corporate tax rate to 25 percent.
Santorum: Triple the personal exemption for dependent children, reduce the number of tax brackets to two — 10 percent and 28 percent — exempt domestic manufacturers from the corporate tax and halve the top rate for other business.
Gingrich: Supports extending and strengthening investigative powers of Patriot Act. Supports continued use of Guantanamo Bay detention for suspected terrorists. Supported creation of Homeland Security apparatus. In 2009, said of waterboarding: "It's not something we should do."
Paul: Opposes Patriot Act as an infringement on liberty. Says terrorists would not be motivated to attack America if the U.S. ended its military presence abroad. Says: "Waterboarding is torture. And it's illegal under international law and under our law. It's also immoral."
Perry: Said it was "unprincipled" for Republicans to vote for creation of the Homeland Security Department. Supports continued use of Guantanamo Bay detention for suspected terrorists. Said U.S. interrogators should "use any technique" short of torture, which he did not define.
Romney: No constitutional rights for foreign terrorism suspects. Campaign says he does not consider waterboarding to be torture.
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