In his speeches to last weekend’s Gridiron Club and to a White House ceremony marking the six-month observance of the terrorist attacks, President Bush struck a somber tone.

His Gridiron remarks, while humorous at the outset, concluded by paying tribute to U.S. soldiers killed in Afghanistan and invoking the murder of journalist Daniel Pearl.

And in speaking Monday to a South Lawn crowd that included an array of America’s anti-terrorism allies, he characterized the last six months as “a short time in a long struggle,” noting that “our war on terror will be judged by its finish, not by its start.”

The president’s manner reflected a sharp contrast with the good-natured jauntiness that often marked his demeanor before Sept. 11 and with the “dead or alive” defiance in the days that followed.

It symbolized the fact that Mr. Bush and his administration have embarked on a more difficult period in which success abroad may prove more difficult and opposition at home more likely.

To be sure, Mr. Bush continues to enjoy strong bipartisan support for his leadership of the war on terror and for his overall conduct of the presidency.

He also may gain the political benefit of an early end to the recession that threatened serious fiscal problems and a potentially problematical political climate for November’s midterm elections.

Still, the atmosphere is very different today from the days following Sept. 11, when the Republican administration reached out to Democrats and Democratic leaders rallied around the president.

While not quite politics as usual, differences between the parties which were set aside in those tense days have re-emerged.

That always has been the way things have worked in Washington, even during such prior national crises as the darkest days of World War II.

Besides, real differences persist in virtually every policy aspect of the war against terrorism, outside the need to counter and retaliate against the terrorists themselves.

Those differences concern the size and nature of economic stimulus measures, the federal role in enhancing airline security, the degree to which civil liberties should be restricted in the search for suspected terrorists, and the size of any defense buildup.

The administration compromised with congressional Democrats on airline security legislation and a recent measure to extend unemployment benefits and provide limited economic stimulus.

But divisions have been even more evident, and compromise has proved more difficult, in the parts of the political agenda that fall outside the war on terror.

They include Mr. Bush’s choices of conservatives for lifetime judicial posts, the dispute on drilling in the Arctic National Wildlife Reserve and the president’s effort to curb domestic spending to pay for defense and homeland security.

Normal partisan acrimony has been exacerbated by the eagerness of such Bush congressional defenders as Sen. Trent Lott, R-Miss., to cast critics in an anti-patriotic light.

That is what happened when Senate Majority Leader Tom Daschle, D-S.D., suggested that the administration needed a clearer road map for the next stage of the war and noted that such initial goals as the capture of Osama bin Laden hadn’t been achieved yet.

For now, despite the increasing uncertainty of future events reflected in Mr. Bush’s tone, the administration is in a very strong position politically.

It has the solid support of the public. So press complaints about receiving inadequate military information don’t draw much sympathy, nor do the questions critics have raised on more defense spending and the administration’s domestic detention policies.

Carl P. Leubsdorf is Washington bureau chief of the Dallas Morning News. His e-mail address is cleubsdorf@dallasnews.com.