WASHINGTON — Karl Rove, the president's chief political adviser, is struggling to steer the Republican Party to victory this fall at a time when he appears to have the least political authority since he came to Washington, party officials said.

Rove remains a dominant adviser to President Bush, administration officials say. But outside the White House, as President Bush's popularity has waned, and as questions have arisen among Republicans about the White House's political acumen, the party's candidates are going their own way in this difficult election season far more than they have in any other campaign Rove has overseen.

Some are disregarding Rove's advice, despite his reputation as the nation's premier strategist. They are criticizing Bush or his policies. They are avoiding public events with the president and Rove.

Influential conservative commentators have openly broken with the White House, calling into question the continued enthusiasm of evangelicals, economic conservatives and other groups that Rove has counted on to win elections. Some Republicans are ignoring Rove's efforts to hold the party together on issues like immigration and Iraq.

In a reflection of this difficult environment, the White House has decided to concentrate nearly all of its resources on the critical fight to keep control of Congress, party officials said, largely stepping away from the governors' races, at least for now.

In Michigan last week, Dick DeVos, a Republican candidate for governor and a longtime contributor to Bush, startled national Republican Party leaders with a searing attack on the president for failing to meet with the leaders of the Big Three automakers. "We're being ignored here in Michigan by the White House, and it has got to stop," DeVos said.

His communications director, John Truscott, said the attack was timed to coincide with Rove's visit to Michigan for a fund-raiser, in an effort to goad Bush into a response. Asked if the DeVos campaign was worried about angering Rove, Truscott said, "That never even crossed our mind."

Rep. Thomas M. Davis 3rd of Virginia, who was chairman of the congressional Republican campaign committee in 2002, said Rove and the White House seemed measurably less involved this year.

"It's been more of a bunker mentality, don't you think?" Davis said. "They have been good in terms of raising the money. The problem is, you have a president with a 38 percent approval rating, and it just changes the dynamics of what they can do."

This midterm election presents Rove with a particularly difficult challenge. Beyond testing his reputation for always finding a way to win, the outcome could determine the extent of Bush's influence for the rest of his presidency and shape the way he is perceived by history. Rove has warned associates that a Democratic takeover in Congress would mean an end to Bush's legislative hopes and invite two years of potentially crippling investigations into the administration.