Sen. Jon Tester, D-Mont., faces a potentially tough re-election bid. Win McNamee/Getty Images hide caption

itoggle caption Win McNamee/Getty Images

Former Massachusetts Gov. Mitt Romney gives a victory speech Tuesday in Novi, Mich., after winning the state's primary. Gerald Herbert/AP hide caption

itoggle caption Gerald Herbert/AP

A line of people wait outside the 11th U.S. Circuit Court of Appeals, which heard arguments over tough new laws targeting illegal immigration in Alabama and Georgia on Thursday. John Amis/AP hide caption

itoggle caption John Amis/AP

A Colombian police officer stands guard next to seized Chinese-made AK-47 replicas on Nov. 18, 2009. The guns have become so ubiquitous around the world that Russia's planned redesign may not do much to booster sales. Luis Robayo/Getty Images hide caption

itoggle caption Luis Robayo/Getty Images

Syrian mourners in Qusayr, a few miles outside Homs, carry the body of a man killed by shrapnel, during his funeral on Tuesday. After a month-long assault by the Syrian army, rebels were forced to retreat from Homs on Thursday. Gianluigi Guercia/AFP/Getty Images hide caption

itoggle caption Gianluigi Guercia/AFP/Getty Images

Students hoping for a repeal of California's ban on affirmative action in college admissions protest outside of the 9th U.S. Circuit Court of Appeals in San Francisco on Feb. 13. The Supreme Court will decide an affirmative action case next fall that could affect college admissions policies across the country. Justin Sullivan/Getty Images hide caption

itoggle caption Justin Sullivan/Getty Images

Police restrain a student protesting against education cuts during a rally in Valencia, in eastern Spain, on Feb. 20. Spaniards are beginning to feel the effects of $20 billion in austerity measures, and discontent is growing. Juan Carlos Cardenas/EPA/Landov hide caption

itoggle caption Juan Carlos Cardenas/EPA/Landov