Cindy McCain CAUGHT CHEATING On John McCain !!!

The ENQUIRER's exclusive bombshell expose as Sen. John McCain's wife, Cindy, is caught with another man!

Not only that but multiple witnesses have caught the pair lip locking on several other occasions.

"I couldn't believe I was watching Cindy McCain passionately kissing and hugging another man!"

That's the stunned reaction of an eyewitness who says he watched in shock - and snapped photos - as the former presidential candidate's wife romantically kissed a long-haired man who resembles "a washed-up '80s rock musician."

Sources told The ENQUIRER investigative team the pair have been seen at concerts and sporting events acting very lovey-dovey

The wealthy blonde heiress and her secret pal have been spotted together around her hometown of Phoenix, Arizona over the past several years, say sources.

The amazing spy photos were snapped April 1, 2006 when Cindy and her companion attended the Tempe Music Festival says the person who took them. The photos are somewhat grainy, but the insider says they depict Senator John McCain's wife, who was greeted by pals at the event as "Cindy."

"To my amazement, Cindy had her hand on his shoulder and was kissing him passionately on his lips," the photog told THE ENQUIRER.

A second witness spotted Cindy and her "mystery man" at a Moody Blues concert "passionately kissing and hugging."

"I couldn't believe it. I remember thinking, 'Go get a room!'

"They kissed and cuddled. While other concertgoers stood up to cheer and sing, Cindy and the guy remained entwined in their seats," the eyewitness said.

While a McCain spokesperson declined comment, for the record, there's a simple matter of math - an 18-year age difference between John McCain, 72 and Cindy, 54.

And while she appeared faithfully by his side at countless campaign rallies, insiders wonder whether she has always been standing by her man.

For the full story and more WORLD EXCLUSIVE PHOTOS pick up the latest ENQUIRER.