One person close to Runyan said the congressman wasn't enamored of Congress and wanted to spend more time with his high school- and middle school-age children. Runyan's son, Jon Jr., recently committed to play football for his alma mater, the University of Michigan, starting in 2015.
His district is likely to be targeted by Democrats in 2014. It went for President Obama in both 2012 and 2008, with Obama getting 52 and 51 percent, respectively.
The district has been rated by the Cook Political Report as "likely Republican." It is now likely to be a toss-up.
An official announcement is expected later Wednesday.
Update 11:12 a.m.: Runyan's office confirms his retirement in a statement from the congressman. Here it is, in full:
"After a great deal of thought and discussions with my family, I have decided not to seek re-election in 2014. Politics shouldn't be a career and I never intended to make it one. While it has truly been an honor to serve the people of New Jersey’s 3rd congressional District, at this stage in my life, and more importantly, the lives of my three children, spending time with them is my top priority. As I serve out the rest of my term, I will continue to work hard on behalf of the people of South Jersey."