JACKSON, Miss. (AP) — Former U.S. Sen. Thad Cochran, who served 45 years in Washington and used seniority to steer billions of dollars to his home state of Mississippi, has died. He was 81.

Cochran's final chief of staff, Brad White, said Cochran died Thursday at a veterans' nursing home in Oxford, Mississippi.

"I've never known a more powerful man, nor a more humble man — a true Southern gentleman that loved the great state of Mississippi," White said.

Cochran was elected to the U.S. House in 1972. When he won a Senate seat in 1978, he became the first Republican since Reconstruction to win statewide office in Mississippi.

He led the Appropriations Committee in 2005-06, channeling more than $100 billion to Mississippi and other Gulf Coast states for Hurricane Katrina recovery after the 2005 storm, and regained the committee chairmanship in January 2015, when the GOP again took control of the Senate.

Cochran won reelection in 2014, but announced in 2018 that he was retiring because of his health.

Republican U.S. Sen. Roger Wicker of Mississippi said Thursday that Cochran was "a dear personal friend for decades."

"Thad Cochran was a giant in the United States Senate and one of the greatest champions Mississippi has ever known," said Wicker, who was elected to the U.S. House in 1994 and has served in the Senate since 2007.

"When Thad Cochran left the Senate, I was reminded of Henry Wadsworth Longfellow, who wrote, 'Lives of great men all remind us we can make our lives sublime, and departing leave behind us footprints on the sands of time,' Wicker said.

Cochran was also a big practitioner of earmarks — home-state goodies such as highway projects, economic development grants and university research dollars.

GOP leaders banned earmarking, but Cochran backed Navy shipbuilding efforts in 2015. Ingalls Shipbuilding in Pascagoula, which makes Navy ships, has long been one of Mississippi's largest private employers.

Mild-mannered and known for working across party lines, Cochran won most of his re-election campaigns easily. However, he struggled in 2014 amid a Republican primary challenge from state Sen. Chris McDaniel, a tea party favorite who had financial support from libertarian-leaning national groups that criticized Cochran as a big spender.

The campaign turned ugly as his opponent's supporters photographed Cochran's bedridden wife, without permission, in the nursing home where she had lived a dozen years with dementia. Images of Rose Cochran were posted briefly online in a video that attempted to show Cochran was having an inappropriate relationship with one of his longtime staff members, Kay Webber — an accusation that Cochran denied.

Weeks after four men were arrested and charged in the photo case, Cochran placed second, behind McDaniel, in a three-person Republican primary. During the three-week runoff campaign, Cochran sought support from a wide variety of voters, including African Americans who traditionally vote for Democrats.

Cochran defeated McDaniel in the runoff, but McDaniel never conceded. Instead, McDaniel filed a lawsuit trying to overturn the results. He claimed the election was tainted because people who never intended to support the Republican nominee in the general election had voted in the party primary. A judge dismissed the lawsuit, saying McDaniel had waited too long to file it, and the state Supreme Court upheld that decision.

In November 2014, Cochran defeated Democratic former U.S. Rep. Travis Childers and the Reform Party's Shawn O'Hara.

Rose Cochran died in December 2014, weeks after the election and before her husband was sworn in for his seventh six-year term in the Senate.

On May 23, 2015, Thad Cochran married Webber in a small ceremony in Gulfport, Mississippi.

During his second stint as Appropriations Committee chairman starting in 2015, Cochran continued working to send money to Mississippi. He and Wicker successfully pushed to get a national historic landmark designation for the home of Medgar Evers, the Mississippi NAACP leader who was assassinated in 1963 outside the house in Jackson.

When Cochran retired, Republican Gov. Phil Bryant appointed the state's Republican Agriculture Commissioner Cindy Hyde-Smith to temporarily succeed him in the Senate. Hyde-Smith was inaugurated in April 2018, then won a special election in November to complete the six-year term that expires in January 2021.

Thad Cochran was born in the small town of Pontotoc, in north Mississippi, and grew up in a suburb of Jackson. He earned a bachelor's degree and law degree from the University of Mississippi. He was an Ole Miss cheerleader as an undergraduate.

Cochran spent three years in the Navy and studied international law for a year at Trinity College in Dublin, Ireland, before moving to Jackson, where he was in a private law practice for seven years before being elected to the House.