A source told the gossip column that Shriver has been involved with Matthew Dowd for years. He was Schwarzengger's longtime campaign strategist when he was governor of California.
The couple recently attended Bobby Kennedy's nuptials to Cheryl Hines together, but this isn't a new dating situation.
The insider claimed, "Maria likes to make it appear that she's the victim, but she's not. The [idea] that they started dating recently is ridiculous."
The source is claiming their affair goes back to 2006 when Dowd was a part of her husband's re-election campaign. They allegedly were open about their fling in front of staffers, so it was not a secret to anyone in the office.
A former campaign worker revealed, "There was a lot of flirtation. 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 eventually found out about his wife's indiscretions and pushed Dowd out of his campaign.
Dowd responded to Page Six's allegations with a direct-message tweet, "There was no affair. We were good friends."
Dowd, who now works as an ABC analyst, has often been on This Week at the same time as the former governor. The network had to give the men separate greenrooms so they wouldn't cross paths.
Schwarzenegger had his own messy affair exposed in 2011, when his love child was revealed and the mother turned out to be the family housekeeper. Shriver has yet to finalize her divorce from the actor, but Page Six's source said it's being handled "amicably."
The reps for the former couple had no comment to Page Six.
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