President Joe Biden's cognitive and physical decline was on full display for years for any reasonable person to acknowledge and notice -- except for most Democrats and members of Biden's inner circle, including his family.

But as many speculated, former First Lady Jill Biden was apparently running the show, to some degree. According to Fox News, a new book described Jill Biden as one of her husband's "chief deniers" while she steadily rose to become one of the most powerful first ladies in White House history.

In other words, Jill Biden -- who knows her husband better than anyone -- was well aware of his decline, but decided to turn the other way so as to benefit her political rise.

The new book seemingly reveals a lot that the Biden family presumably didn't want the public to know.

What's going on?

The book, "Original Sin," authored by CNN anchor Jake Tapper and Axios political correspondent Alex Thompson, provided an inside look at what was really going on behind the scenes as Joe Biden struggled to maintain a healthy appearance.

The two authors detailed how Jill Biden went from reluctant presidential spouse to one of the most powerful to ever hold the title of First Lady.

Fox News noted:

Jill Biden, who has a doctoral degree in education and whom White House staffers called "Dr. B" for short, was a reluctant political spouse in the early days of her husband's career. During his presidential campaigns and into his presidency, the first lady became his staunchest defender and a "political partner in addition to a spouse," Thompson and Tapper wrote.

Tapper and Thompson explained, "Dr. B was a strong, protective force in the White House. She was also, without question, one of the chief supporters of the president's decision to run for reelection, and one of the chief deniers of his deterioration."

They also pointed out that Jill Biden had a heavy influence on Biden's campaign activities and his overall public appearance.

"She weighed in on potential hires and reviewed many of the campaign ads before they were aired. She campaigned hard and peppered aides with questions about how many reporters would be at her events," the authors wrote.

She "kept score"

Jill Biden was so involved in the decision-making process that she even reportedly sat in on interviews with prospective White House aides.

She also apparently "kept score" as to who her husband's most loyal aides were.

The book is just further proof of what many speculated about Jill Biden's role in covering for her husband.

Only time will tell what else is revealed.