By RYAN GORMAN
Maria Shriver was having an affair long before husband Arnold Schwarzenegger revealed his love child, according to a new bombshell report.
Shriver was sleeping with Matthew Dowd, Arnie's campaign strategist in 2006, five years before her actor-turned-politician hubby's philandering was outed, sources tell the New York Post.
Dowd and Shriver reportedly did not make much of an effort to hide their illicit romance, and often flirted in front of her husband's staffers while he ran for re-election in California's 2006 gubernatorial campaign.
"There was a lot of flirtation," a former campaign staffer told the Post. "They frequently spent time alone, and Arnold was rarely, if ever, around when they were together.
"She had a unique banter with [Dowd] and lit up when he was around. He was comfortable poking fun at her, and she would slap him teasingly."
Schwarzenegger, 67, soon caught onto Dowd bedding his wife and muscled him off the campaign – but he and Shriver, 58, often argued about the affair.
"They were having blowouts in public over Matthew. Yelling and crying. Total chaos," another source told the paper. "I was like, 'How are we going to keep this from getting out?'"
Dowd, 53, has denied the affair to the Post, but he and Shriver recently attended cousin Bobby Kennedy's wedding.
"Maria likes to make it appear that she's the victim, but she's not," another anonymous source told the paper. "The [idea] that they started dating recently is ridiculous.''
Shriver is said to have traveled all over the country to see Dowd while her hubby was toiling away in the state capitol Sacramento. The pair stayed at the Four Season in New York in 2007, and also in a beachside hotel in Santa Monica, sources insisted.
Schwarzenegger reportedly knew about the affair, and even requested a separate green room when he and Dowd appeared on ABC's "This Week" in 2010.
Arnie and his Kennedy-heiress wife maintained a public persona of togetherness for years until his affair with a housekeeper and the love child he fathered were revealed in 2011.
Now 16-years-old, Joseph Baena was fathered by the hulking actor with family housekeeper Mildred Baena, according to reports. The teen's existence became public 13 years after he was born.
Joseph Baena recently attended the premier of Schwarzenegger's latest movie, "Expendables 3."
Shriver split with him to stay in a hotel and Dowd drunkenly bragged about staying with her in a hotel after downing a few too many cocktails at a wedding later that year.
Dowd has since joined ABC News as a political correspondent.
Shriver and Schwarzenegger are still in the process of settling their divorce. Both declined to comment on the report.
Will Brad and Angie's wedding photo money money go to charity?
Jennifer Lawrence requests investigation into photo leak
Nude photos of Jennifer Lawrence and other major celebrities leak online