Karl Rove, close political adviser to U.S. President George W. Bush and a lightning rod for anger among Democrats, has said he will leave the White House at the end of this month.
A White House spokeswoman confirmed to Reuters that Rove would quit in late August, describing it as a "big loss".
"I just think it's time," Rove said in an interview with the Wall Street Journal published on Monday.
"There's always something that can keep you here and, as much as I'd like to be here, I've got to do this for the sake of my family."
Rove, the White House deputy chief of staff known as "the Architect" for his campaign skills, is the latest in a series of senior Bush aides to quit in recent months.
Earlier this month, Bush set up a possible court showdown with Democratic lawmakers by citing executive privilege in rejecting a subpoena for Rove to appear before the Senate Judiciary Committee in a probe over fired federal prosecutors.
Bush's opponents have sought to force Rove and other aides to testify about the firing last year of nine U.S. prosecutors.
Democrats say the firings may have been intended to influence investigations of Democratic or Republican lawmakers. Bush and Attorney General Alberto Gonzales, who signed off on the firings, have said they were justified but mishandled.
Gonzales also faces calls for a perjury investigation over the truthfulness of his testimony to Congress about the firings and a warrantless domestic spying program.
The Journal said Rove had first put out the idea of resigning a year ago, but delayed leaving as the Democrats won control of Congress late last year and then as the White House faced debates about immigration and the Iraq war.
Rove finally decided to leave after Joshua Bolten, the White House chief of staff, told senior aides that if they remained past early September, they would be obliged to stay until the end of Bush's second and final term in January 2009, the paper said.
Rove, who was chief strategist of Bush's presidential campaign in 2000, has had a senior post in the White House since Bush took office in January 2001.
The Journal said Rove was planning to return to Texas, as he and his wife have a home in Ingram and a son attending college in San Antonio.