Four states will decide the winner of Republican primary elections Tuesday, with the Kansas race drawing special attention. 

In Kansas, voters will decide whether to choose a veteran U.S. senator or a physician who has distant ties to President Barack Obama. 

According to Reuters, the Republican race in Kansas' 4th Congressional District between Republican Todd Tiahrt and incumbent U.S. Rep. Mike Pompeo may come down to a food labeling issue. 

Pompeo, who has the support of food and agriculture companies, introduced a bill that would halt state efforts to require labeling on foods that are genetically modified. Tiahrt has garnered support by conflicting with Pompeo on the issue and supporting the food labeling, which is a law that is being sought in a number of states. 

Michael Smith, a professor of political science at Emporia State University, said Tiahrt is running a "'scorched earth' policy of attacking many traditional Republican donors."

Pompeo joined the U.S. House of Representatives when Tiahrt lost his Senate seat in an unsuccessful election in 2010. 

Republican Sen. Pat Roberts, who has been in Congress for 47 years, is also facing a election battle against conservative Tea Party candidate Milton Wolf, a doctor who claims he wants to "save the Republic."

Wolf has distant familial ties to Obama, but is running on a platform that focuses on repealing Obama's policies. When interviewed by CNN, Wolf said he promised the "mother of all family feuds to save America," if he is elected. 

Michigan, Missouri and Washington are also holding primary elections Tuesday. 

In Michigan, reindeer farmer and Santa Claus impersonator Rep. Kerry Bentivolio looks set to lose against challenger Dave Trott. Bentivolio's loss will make him the third incumbent Republican congressman to lose a primary election this year. 

Also, incumbent U.S. Republican Rep. Justin Amash and challenger Brian Ellis will go head-to-head in the Michigan primary. Amash, a Tea Party favorite, is a member of a group of House conservatives who are known for their unwillingness to compromise. Conversely, Ellis, the head of an investment firm, calls himself "West Michigan Nice," because he is known for his affable demeanor and willingness to cooperative with political foes. 

In Missouri, John "Jay" Ashcroft, whose father John Ashcroft was Missouri governor, U.S. attorney general and a U.S. senator, is up for election for the state senate. 

Five U.S. representatives in Missouri will face primary challenges, but are expected to retain their seats prior to November's midterm election. 

Pedro Celis is challenging frequent political candidate "Mike the Mover," formerly known as Michael Shanks, in Washington state's 1st Congressional District. Celis is the former chairman of the Republican National Hispanic Assembly, and is expected to win the primary election. If he wins as expected, he will go up against incumbent Democrat U.S. Rep. Susan DelBene in November. 

According to a recent CBS News/New York Times survey, Republicans are poised to take over the Senate in November's midterm elections. According to the poll, Republican candidates are favored in contested swing states. Yet, while the Senate will definitely be divided in 2015, a Republican majority is not guaranteed, as they are favored to win by a slim margin.