California’s Orange County is at the epicenter of Democrats’ fight to take control of the House in November, and the 48th Congressional District is the heart of the traditionally Republican bastion in blue California.

The district, represented by Republican Dana Rohrabacher, is one of the 23 Republican-held districts that voted for Hillary Clinton in 2016, and Democrats see it as a possible pickup opportunity in the general election as talk of a "blue wave" in Southern California intensified in neighboring districts.

Rohrabacher is seeking a 16th term in office -- he's been in Congress for three decades -- but he is just out of his toughest primary yet, where 15 candidates aimed to unseat him and is far from having a tight grip on his seat.

Rohrabacher, a fixture of Republican politics -- he was Ronald Reagan’s speechwriter -- and generally a staunch supporter of Trump, is a controversial figure. His name has repeatedly surfaced in connection with the investigation into Russian meddling in the 2016 election, and his ties and contacts with Russian nationals and operatives have come under intense scrutiny.

Democrat Harley Rouda narrowly won a spot on the ballot after a boost from the Democratic Congressional Campaign Committee, which endorsed him mere weeks before the primary.

The primary victory by Rouda, an ex-Republican business executive, over fellow Democrat Hans Keirstead, further put under scrutiny the role national organizations have in local races -- evidence of party infighting as Democrats focus on flipping the House in November.

Republican candidate

Rep. Dana Rohrabacher: Incumbent U.S. representative | Age: 71 (June 21, 1947)

Democratic candidate

Harley Rouda: Businessman | Age: N/A

18 For 18’ is ABC News’ powerhouse political coverage of the 2018 midterm elections. To stay up to date, visit ABCNews.com, the ABC News app, and follow our midterm elections alerts.