Sen. Arlen Specter, R-Pa., said Stickler wasn't the "right man for the job."
Sen. Edward Kennedy, D-Mass., warned that Stickler was a bad choice.
"He has shown over and over again that safety is his last priority," Kennedy said.
More than two weeks after six miners were trapped deep underground in a Utah coal mine, critics are questioning Stickler's leadership of the Mine Safety and Health Administration in light of the tragedy that has already cost the lives of three rescue workers and likely the six miners.
At the same time, Stickler is not without supporters.
"Richard Stickler is a very competent MSHA official," Sen. Orrin Hatch said. "He has done his best to see that the job is done right. He cares greatly about these miners."
Still, Wanda Blevins, whose husband, David, died in the Jim Walter Resources mine tragedy in 2001, fought Stickler's nomination before Congress and says the Utah disaster proves why she opposed Stickler.
"He was wrong from the start," Blevins said. "He's still wrong today."
Debbie Hamner, whose husband, George "Junior" Hamner, was one of 12 miners killed in the Sago mine disaster in 2006, says that Stickler is carrying through with the Bush administration's agenda to ensure productivity in coal mines.
"Under the Bush administration, I just feel that production is more important than human life," Hamner said. "Bush has set the stage for all these accidents to start happening now. There's going to be more if MSHA doesn't start doing their job."
Rep. Lynn Woolsey, a California Democrat who heads the House subcommittee overseeing worker safety, said in an interview she places some blame for the mine disaster on the Bush administration and leadership of MSHA.
"I believe they are partly at fault," Woolsey said. The practice of retreat mining - in which workers remove sections of coal holding up walls as they leave a mine area, a practice that was being done at the Crandall Canyon mine - was not a safe activity, she maintained. "That has to be known before you send individuals into danger."
Stickler, a former underground miner himself, rose quickly in the industry, eventually reaching executive status before leaving to head Pennsylvania's mine safety agency. President Bush tapped the then-retired Stickler last year to head MSHA, but several senators balked, including Kennedy - who charged that when Stickler was a senior manager at a mine in West Virginia, the injury rate was three times the national average.
Kennedy also argued that when Stickler ran the Marianna mine, the injury rate climbed "dramatically" and that mines he managed before heading the Pennsylvania Bureau of Deep Mining had a total of 3,000 safety violations.
MSHA and Stickler's supporters dispute those statistics. Stickler also said current laws were "adequate" when asked about changing regulations with the MINER Act, a sweeping overhaul of mine laws that passed overwhelmingly last year.
The Senate twice sent Stickler's nomination back to Bush.
But when Congress left town last October for a break, Bush used his power to temporarily put Stickler in charge of MSHA. His recess appointment ends this year. A formal confirmation by the Senate may be unlikely now after the Utah disaster.
Sen. Robert Byrd, D-W.Va., placed a "hold" on Stickler's full nomination and said this week the quality of MSHA's investigation and resulting actions with the Utah disaster - and one in Indiana that killed three miners - will "undoubtedly be a test of Richard Stickler's leadership and worthiness to be properly confirmed" by the Senate.
"I continue to be very concerned about the slow implementation of the MINER Act and other mine safety improvements," Byrd said, referring to legislation passed in the wake of the Sago mine accident in West Virginia that killed 12 miners. That measure triggered the largest overhaul of mining regulations in three decades, though critics say many of the provisions have not been implemented quickly enough.
"I am paying very careful attention to the developing situation in Utah to see if those concerns are being addressed," Byrd added.
Stickler, who has been at the Crandall Canyon mine since the disaster happened on Aug. 6, could not be reached for comment on this story. The Department of Labor pointed to a fact sheet that says he is a "proven leader" and has worked hard to implement safety regulations.
The department also said that when Stickler headed the Pennsylvania mine safety office, mine injuries decreased in the state. And now, as head of MSHA, the agency issued eight "pattern of violation" warnings - its most severe admonishment - to mines in June.
Sharp's Point - a subscription e-newsletter on the mine industry - quoted Dennis O'Dell, a top official with the United Mine Workers of America, this month saying that Stickler was "doing a helluva job."
Phil Smith, a spokesman for the union, says it's "entirely possible" O'Dell said that. But MSHA's record has changed with the Crandall Canyon mine. "There have been things exposed that concern us a great deal," Smith said.
Smith also pointed out that the agency's approval of a "flawed plan at best" to allow retreat mining at the Utah mine raises concerns about Stickler's leadership of MSHA.
"This demonstrates that the culture at MSHA has not changed in a way we were concerned it would not with [Stickler's] appointment," Smith says.
But Stickler continues to enjoy support from Hatch and other Republican officials.
Wyoming Sen. Michael Enzi lobbied for Stickler to be confirmed last year, saying that the three-generation coal miner has more than 37 years of mining experience, including as an underground miner, captain of a mine rescue team and superintendent and mine manager.
"I believe there could be no one better to implement these changes than a former mine rescue team captain," Enzi said.
* Assistant Secretary of Labor, director of the Mine Safety and Health Administration, Oct. 13, 2006 - present.
* Director, Pennsylvania Bureau of Deep Mine Safety, 1997-2003; worked in the command center at the Quecreek Mine in Pennsylvania rescue operation in 2002.
* Started as underground coal miner at a BethEnergy mine in West Virginia and moved up in rank, eventually serving as the company's manager.
* Bachelor's in general engineering, Fairmont State University.
* Mine safety professional, International Society of Mine Safety Professionals.
Source: Mine Safety and Health Administration and news