A 1986 graduate of Fairfax High School, Chap is also a graduate of Williams College and the University of Virginia Law School. During law school, he clerked for the U.S. Attorney's office in Charlottesville, winning his first trial at the age of 25. He has been in private practice since 1994 and is currently a partner with the law firm of Bracewell & Patterson, LLP. His specialty is representing honest people and obtaining justice for them.

After finishing school and starting his practice, Chap returned to his hometown of Fairfax City. In 1998, the voters elected Chap to serve as their City Councilman. He was re-elected in 2000. During that time, he served as the City's representative on the Northern Virginia Regional Commission.

In 2001, Chap won the State Delegate seat for the 37th District, defeating the long-time incumbent in a major upset. In a 2003 rematch, the Republican party targeted the 37th District. However, in a featured contest dubbed a "race to watch" by the Virginia Political Action Project, Fairfax voters returned Chap with 60% of the vote.

In December 2003, Minority Leader Frank Hall named Chap as a Democratic House Whip. In addition to those duties, Chap sits on the Science and Public Safety Committees, and participates in various legislative commissions.

Chap, his wife Sharon and their two daughters, Eva (5) and Mary Walton (2), live in Fairfax City, a couple blocks from the historic downtown. Chap and Sharon are members of Truro Episcopal Church. Chap is active with the Good News Jail & Prison Ministry, which provides Christian-based education and counseling to inmates at the Fairfax County jail. Sharon is a practicing attorney, full-time mother and part-time field hockey coach at Fairfax High School. When not serving in the Assembly, Chap enjoys outdoor sports, playing rugby for the Northern Virginia Rugby Football Club, and spending time with his family.