Nearly two weeks after the death of her husband Sen. John McCain, Cindy McCain penned an op-ed for USA Today calling on Americans to serve a cause greater than themselves.

That was the "essence" of John McCain's message to the country, she wrote.

"That we must join together, shaped by our deepest values of liberty, equal justice and respect for the dignity of all people," Cindy wrote, "hardened by unwavering courage and integrity, and step into the arena to fight for a greater cause."

She said her husband fought for a greater cause "every day."

"John McCain fought for others every day of his life, whether he was wearing a uniform or standing on the floor of the U.S. Senate," she wrote.

Cindy McCain said with husband's death the country "inherently understood that this is the kind of leadership we want."

"That this is the kind of country we want to be," she wrote. "And that it is now up to us — all of us — to get into the arena and fight. Each of us must do something to fight for a greater cause. We can lead, we can support, we can contribute, we can donate — but we must do something."

Inspired by her husband's memory, Cindy McCain said the McCain Institute for International Leadership is her "home now" and where she will fight for the values held so dear by her husband.

She said she wants Americans to join her in fighting for what is right.

"Since his passing, thousands of people have asked how they can do something to honor Sen. McCain," she wrote. "I’ll tell you how: Join me in the arena. Fight for a greater cause."