Garcia said he spoke with Whitesides to congratulate him on Monday.
"Representing the people of California's 27th Congressional District the last 4.5 years has been an honor of a lifetime," Garcia said in a statement issued by his campaign. "I want to thank my family for making the sacrifices, and my team and my volunteers for working harder than any other team in the nation during this journey of providence. We achieved so much in a short period of time. We truly made history and saved lives. I'm proud of all we've done."
Garcia facing challenge from Whitesides in 27th district
George Whitesides says Congressman Mike Garcia is 'too extreme' for CA-27 congressional district
Whitesides called his election "the honor of a lifetime" and thanked Garcia for his service to the district.
"In Congress, you can count on me to fight to create more good local jobs, lower everyday costs, build safe communities, protect Social Security and Medicare, and protect reproductive freedom," Whitesides said.
The seat was one of a handful of tight races around the country seen as possibly tipping the partisan balance in the House of Representatives.
As of Monday afternoon the Associated Press was reporting that Republicans were four seats away from securing control of Congress, with less than 20 races left to be called.
The 27th Congressional District includes the Santa Clarita and Antelope valleys.
Results posted by the Los Angeles County Registrar-Recorder/County Clerk indicate Whiteside was leading by about 7,000 votes out of more than 288,000 cast, for a 51.2% to 48.8% lead.