Reportedly MARIA SHRIVER was having an affair when still married to love-rat hubby Governator Arnold Schwarzenegger.

After Matthew Dowd recently squired Maria Shriver to RFK Jr.’s wedding, insiders pointed that she’d actually had an affair with Dowd, a former member of Arnold’s campaign, well before the couple’s 2011 announcement they were splitting.

“Maria likes to make it appear that she’s the victim, but she’s not,” a source told the NY Post “The [notion] that they started dating recently is ridiculous.’’

ABC politics analyst Dowd, 53, functioned as a strategy advisor for the Austrian-born bodybuilding icon during his time in politics. Sources told the paper it was incredulous that Shriver, 58, was acting as if they had just started dating during their appearance at the Kennedy wedding.

According to insiders, Shriver began hooking up with Dowd in 2006, and did little to downplay her romance, or chemistry, with the politico in front of campaign insiders. “There was a lot of flirtation,” a campaign source told the paper. “They frequently spent time alone, and Arnold was rarely, if ever, around when they were together.

“She had a unique banter with him and lit up when he was around. He was comfortable poking fun at her, and she would slap him teasingly.”

When The Terminator finally was alerted to Shriver’s infidelity, sources told the paper, he distanced himself from Dowd, causing “public blowouts,” “yelling and crying,” and “total chaos” between him and his estranged spouse, creating a divide between campaign staffers, choosing them to essentially take sides while working overtime to quell the damaging news from leaking. “I was like, ‘How are we going to keep from getting out?’” the staffer told the NY tab.

Even after Dowd was removed from the campaign, his relationship with Shriver continued, and insiders said he’d even boasted about making love to a Kennedy family member. “She referred to him as one of her closest friends,” sources told the Post. “The governor knew about it the whole time.”

When Schwarzenegger’s love child scandal broke out three years ago, the Kindergarten Cop star’s top lieutenant put out word to keep a lid on Maria’s alleged infidelity the Shriver infidelity, as he “did not want the dirty laundry out there,” insiders said.

Dowd told the paper that “there was no affair,’’ and that he and Shriver were just “good friends” at the time.