U.S. Midterm elections: Key Senate battlegrounds The Republicans hope to gain a majority in the U.S. Senate by wresting seats from vulnerable Democrats and taking spots left open by retirements. With the House of Representatives firmly in Republican hands, winning control of the Senate would enable the party to effectively shut down Democratic President Barack Obama's agenda in his last two years in office Independent: 2 Dem 53 SENATE Rep 45 100 seats, 51 seats needed for majority, 37 races at stake Republicans need six seats to regain control MN ME MT WV NH OR ID WY SD MI MA NE IL NJ DE KY VA NM OK TN SC ALASKA TX MS AL HAWAII LA Leaning Democrat Leaning Republican Close races No election COLORADO - Udall v Gardner Democratic incumbent Mark Udall, scion of famous political family, faces young Republican congressman Cory Gardner, from rural east of state, in race that highlights Colorado’s geographic and cultural divisions KANSAS - Roberts v Orman Republican incumbent Pat Roberts, first elected to Senate in 1996, faces independent candidate, businessman Greg Orman, whose chances have been boosted by withdrawal of Democratic Party candidate IOWA - Braley v Ernst Democrat Congressman Bruce Braley initially projected to win seat of agricultural state but now in dead heat with Republican Joni Ernst following slip by Braley in which he appeared to mock farmers ARKANSAS - Pryor v Cotton Democrat Senator Mark Pryor, first elected to Senate in 2002, faces Republican congressman Tom Cotton – veteran of Iraq and Afghanistan and among most conservative members of House GEORGIA - Nunn v Perdue Non-profit executive Michelle Nunn, daughter of long-time U.S. Senator Sam Nunn, is trying to become first Democratic U.S. senator elected in Georgia since 2000. She faces Republican businessman David Perdue N. CAROLINA - Hagan v Tillis Incumbent Democratic Senator Kay Hagan, elected in 2008 amid wave of support for Barack Obama in conservative state, in tight race with Republican Thom Tillis, speaker of state House of Representatives Sources: www.senate.gov, wire agencies Pictures: Associated Press