Patti Solis Doyle has quit her job as Hillary Clinton's presidential campaign manager, but said Sunday she will remain a senior adviser.

In a campaign memo sent to staff, Solis Doyle said she has been on the trail for a year, and the sacrifices have been great.

"This has already been the longest presidential campaign in the history of our nation, and one that has required enormous sacrifices from all of us and our families," Solis Doyle wrote. "I have been proud to manage this campaign, and prouder still to call Hillary my friend for more than 16 years. I know that she will make a great president."

Solis Doyle said Maggie Williams, a senior adviser to the Clinton campaign, will take her place. Solis Doyle said that the transition will be seamless since she and Williams are longtime friends and have been working toward this goal for a month.

Campaign officials told FOX News that Solis Doyle was not asked to step down, and the switch does not signal that the campaign is in any different position than it was the day before. The announcement came one day after Clinton opponent Barack Obama swept three state races -- in Washington, Nebraska and Louisiana.

Shortly after the statement, Clinton issued a statement echoing Solis Doyle's sentiment about the exhaustive toll campaigning takes.

Clinton added that Solis Doyle had "done an extraordinary job in getting us to this point -- within reach of the nomination -- and I am enormously grateful for her friendship and her outstanding work."

Solis Doyle, who will continue to travel occasionally with Clinton, was one of several campaign staffers who agreed to take a pay cut this month as the New York senator tries to keep on par with the fundraising fortune Obama has raised.

Clinton has also tried hard to appeal to Latino voters, and Solis Doyle's departure removes one of the most visible and high-ranking Hispanic-Americans ever on a campaign.

Solis Doyle's appointment as Clinton's presidential campaign manager last year surprised many Democratic operative including some in Clinton's inner circle, who believed she did not have sufficient political experience to run the operation.

Clinton aides loyal to Solis Doyle say she proved the naysayers wrong, smoothly managing a staff of several hundred and a budget that swelled to well over $100 million while leaving most of the campaign's major strategic decisions to others -- particularly Clinton pollster Mark Penn and media adviser Mandy Grunwald.

But she was also criticized by others for, among other things, failing to anticipate and plan for Obama's fundraising prowess.

FOX News' Aaron Bruns and The Associated Press contributed to this report.