Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. Americans Cast Votes, But Not Only for President by Wayne Lee WASHINGTON -- As millions of Americans exercise their right to vote Tuesday to determine the successor to U.S. President Barack Obama, they will also decide who will represent them in the U.S. Senate and in the U.S. House of Representatives. Voters will determine who will fill 34 of the 100 Senate seats and all 435 seats in the House. Republicans now dominate the Senate by a 54-46 margin. Democrats need to capture five seats to constitute a majority. If Democrats gain only four Senate seats and Clinton wins the presidency, her vice president will be able to break any 50-50 tie votes. Republicans are expected to retain control of the House, where they have a 247 to 188 advantage. Republican and Democratic analysts predict Republicans will lose ten to 15 House seats. Political analyst Nathan Gonzales told VOA "control of the Senate is in play" and it is "more likely Democrats will gain control," by winning 3 to 6 Senate seats. But Gonzales added "a Republican majority cannot be ruled out." In the House, Gonzales said Democrats may gain eight to 13 seats. Gonzales said Republican presidential candidate Donald Trump "has been a drag on Republican candidates in major cities." But he said the real estate mogul has not hurt Republican candidates in rural areas. Incumbents, candidates in the running About one third of the Senate seats is up for reelection every two years, and this year Republicans are defending 24 of the 34 seats that are in play. Here is a look at some of the races that will decide which party controls the Senate next year. Arizona: Republican Senator and former presidential candidate John McCain has a commanding lead in the polls over Democratic challenger Ann Kirkpatrick, who currently represents Arizona's largest district in the House. RealClear Politics' polling average has McCain ahead of Kirkpatrick by a 10 percentage point margin. Republican Senator John McCain (2-R) and his wife Cindy McCain (R) greet supporters voting at a polling station in Phoenix, Arizona, Nov. 8, 2016. Some polls show the 2008 presidential candidate leading his Democratic challenger Rep. Ann Kirkpatrick. Florida: Republican Senator and former presidential hopeful Marco Rubio reversed course in June when he announced he would seek reelection after his failed presidential bid. RealClear Politics' polling average shows Rubio leading Democratic Congressman Patrick Murphy by 3.7 percentage points. Illinois: Republican Senator Mark Kirk has inspired supporters as he campaigned in a wheelchair after suffering a stroke in 2012. But Kirk is facing a stiff challenge from Congresswoman Tammy Duckworth, whose narrative is just as compelling. A veteran, Duckworth lost both her legs in 2004 when her helicopter in Iraq was hit by an enemy missile. RealClear Politics' polling average shows Duckworth leading Kirk by 13.3 percentage points. Indiana: Former Democratic senator Evan Bayh announced in July he would attempt to regain his seat. Bayh is being challenged by Congressman Todd Young, whose campaign has received lots of outside financial support from groups such as the U.S. Chamber of Commerce. Young has a slight 0.7 percentage point lead over Bayh, according to RealClear Politics' polling average. Missouri: Democrat Jason Kander, Missouri's secretary of state, is engaged in a tight race with Republican incumbent Senator Roy Bunt. In a state that will likely give Trump a double digit victory, Kander trails Bunt by 1.3 percentage points, according to RealClear Politics' polling average. Nevada: After Senate Minority Leader Harry Reid announced his retirement last March, Republican Congressman Joe Heck challenged former state attorney general Catherine Cortez Masto, who if she wins, would be Nevada's first Latina senator. RealClear Politics' polling average puts Masto ahead by 1.8 percentage points. New Hampshire: Republican Senator Kelly Ayotte and Democratic Governor Maggie Hassan are locked in a tight race. Ayotte has struggled to overcome the effects of Trump's popularity, but is clinging a 1.5 percentage point lead, according to RealClear Politics' polling average. Ohio: Republican Senator Rob Portman is well ahead of former governor Ted Strickland. RealClear Politics' polling average shows Portman enjoying an 18.3 percentage point lead over Strickland. North Carolina: RealClear Politics' polling average shows Republican Senator Richard Burr holding onto a narrow two percentage point lead over Democratic opponent Deborah Ross, a former state legislator with a reputation as a staunch civil rights advocate. Democratic Rep. Tammy Duckworth, an Iraq War veteran who lost both of her legs in combat, acknowledges applause from supporters in Springfield, Illilois, Aug. 20, 2015. Some polls show her ahead in her quest to unseat incumbent Republican Senator Mark Kirk. Pennsylvania: Republican Senator Pat Toomey and Democratic challenger Katie McGinty are deadlocked in what the Philadelphia Inquirer reports is the most expensive Senate contest in the history of Pennsylvania. More than $140 million was spent by the end of October. Wisconsin: First-term Republican Senator Ron Johnson trails Democratic challenger and former senator Russ Feingold by 2.7 percentage points, according to RealClear Politics' polling average. But Johnson has inched closer to Feingold in recent weeks in a state that has not had a Republican candidate win a Senate seat in a presidential election since 1980. The fight for control of the 435 seats in the House of Representatives involves three dozen swing seats. Here are some of the more potentially impactful contests in congressional districts throughout the U.S.: California's 49th District: Eight-term Republican Congressman Darrell Issa, the richest man in Congress is in the fight for his political life against Doug Applegate, who has campaigned as an outsider. ElectionProjection.com shows Applegate ahead by a miniscule 0.2 percentage point. Florida's Seventh District: Seventy-three year-old Republican John Mica is facing a stiff challenge from 38 year-old Democrat Stephanie Murphy. When the district was recently redrawn, Mica was placed into a suburban district with a more racially diverse population that tends to vote Democratic. Minnesota's Eighth District: Democratic Congressman Nick Nolan is trying to fend off Republican challenger Stewart Mills, who unsuccessfully challenged Nolan in 2014. ElectionProjection.com shows Nolan with a two percentage point lead over Mills. Virginia's 10th District: Republican Congresswoman Barbara Comstock is trying to hold onto her seat in a suburb just outside the nation's capital by distancing herself from Donald Trump. Comstock's lead over Democratic challenger LuAnn Bennett is less than one point, according to ElectionProjection.com. Texas' 23rd District: Former Democratic Congressman Pete Gallego is trying to recapture a seat he lost 2014. The seat is in a heavily Latino which covers a long stretch of the U.S. southern border with Mexico. The seat is currently held by Republican William Hurd, an African-American former CIA Agent. Any Republican seeking election in this district may be hindered by strong anti-Trump sentiment. Continued Republican control in the House and the Senate could stymie any Clinton legislative proposals. A Trump victory, coupled with Republican control of both house chambers, could spell an end to Obama's Affordable Care Act, commonly known as Obamacare. Senate members who take office on January 3 will be confronted with several significant issues. They range from filling the vacant seat on the U.S. Supreme Court, immigration reform and free-trade pacts with Pacific Rim countries and Europe.