Emboldened by the ouster of presidential adviser Van Jones, conservative and business groups are launching fresh challenges aimed at derailing President Obama's nominees.
The latest of these targets is David Michaels, Mr. Obama's pick to head the Occupational Safety and Health Administration (OSHA), who as an academic published a book attacking corporate executives for the tactics they used to fight class-action lawsuits. Republican critics said they considered Mr. Michaels to be too close to trial lawyers because of his aggressive advocacy on their behalf.
"We are definitely troubled by Michaels' nomination," said Keith Smith, the director of employment and labor policy and the National Association of Manufacturers. "We will be urging the Senate committee to carefully review his nomination."
The drumbeat of criticism aimed at Mr. Michaels follows a pattern that began with the case of Cass Sunstein, who last week was confirmed by the Senate as the White House's top regulator. Critics attempting to kindle doubts about Mr. Sunstein first outlined their objections on conservative blogs.
Colorful samples from Mr. Sunstein's large body of academic work -- including those suggesting his strong views on animal rights and organ donation -- became fodder for critical commentaries on conservative Op-Ed pages and then arose during right-leaning television and radio talk shows.
Fox News personality Glenn Beck dispatched a message on Twitter seeking more information about Mr. Sunstein.
In Mr. Michaels' case, the objections initially stemmed from his writings on tactics that corporations have used to fend off class-action lawsuits. Later, blog postings expanded on those complaints to include a paper Mr. Michaels wrote airing his strong views about the perils of gun ownership. The blog postings were followed by newspaper columns opposing Mr. Michaels' confirmation.
On Monday came fresh objections, this time from Grover Norquist, founder of the conservative advocacy group Americans for Tax Reform.
"These appointments have all caused a similar reaction," Mr. Norquist said.
"These are not the appointees of an unassuming, moderate, non-ideological guy. These are people with very extreme views."
Mr. Michaels did not respond to telephone and e-mail messages, but White House officials said the attacks leveled at Mr. Michaels and Mr. Sunstein have been strictly partisan, and nothing like those directed at Mr. Jones.
"[Mr. Michaels] is a nationally recognized leader in efforts to ensure the integrity of the science underpinning public health and environmental regulation," White House spokesman Thomas Vietor said.
"These accusations are simply ridiculous and false."
Mr. Jones resigned his post as the president's "green jobs" adviser after video footage captured him comparing President George W. Bush to a crack addict and after his signature surfaced on a petition entertaining the idea that the U.S. government was complicit in the Sept. 11 terrorist attacks.
Mr. Sunstein, by comparison, had backing from some conservative corners and was easily confirmed last week as the administration's new head of information and regulatory affairs.
Mr. Michaels' fate remains uncertain. The Senate committee that will handle his confirmation hearings has not scheduled the proceedings.
Regardless of the outcome, Mr. Norquist said, such cases represent an important shift in Washington.
For several months, he said, many Washington lobbyists and advocacy groups were reluctant to challenge a new administration that was showing widespread public support, and had strong backing from partisan majorities in Congress.
Mr. Norquist said he thinks the summerlong activism in town-hall meetings, rallies across the country, Mr. Jones' resignation, and Mr. Obama's declining poll numbers, have persuaded Republicans to fight presidential nominations that raise strong objections.
"Traditional K Street was paralyzed by fear of the Obama administration," Mr. Norquist said. "The first reaction was, a president who has 60 votes in the Senate can pass anyone he wants, so why complain."
Now, he said, they have realized "it's worth the fight."
It is worth the fight, he said, because at a minimum, it forces members of the Senate to think carefully before casting a vote on someone who may carry some political baggage.
In the case of Mr. Michaels, the concerns have been based largely on his writings about the role of scientific evidence in class-action lawsuits.
In a 2005 article "Doubt Is Their Product," which later became the basis for a book of the same name, Mr. Michaels wrote that the Bush administration had swung open the door for corporate abuse.
"I believe it is fair to say that never in our history have corporate interests been as successful as they are today in shaping science policies to their desires," he wrote.
The problem, said Mr. Smith, of the manufacturers' group, "is that his approach in every case seemed to be to paint employers as a whole as malevolent actors."
That is not a quality that the business community would like in someone responsible for policing workplace safety, he said.
The White House countered that Mr. Michaels is a respected scientist whose work has been widely praised. His resume includes a previous stint doing occupational safety work for the Department of Energy, and years of study on the best methods to tackle workplace regulatory issues.
With an influenza outbreak putting "millions of front line health care workers at risk, we need a respected scientist at the helm of OSHA," Mr. Vietor said.
The president's supporters said Monday they will not sit back idly if they see attempts to torpedo Mr. Obama's nominees.
"We're going to fight back against it," AFL-CIO spokesman Eddie Vale said. "If Obama is picking nominees that are going to be friendly to workers, we're not going to sit back and let big business go after his nominees."