Every White House picks its words carefully, using poll-tested, focus-grouped language to frame issues and ideas to advance its goals. Mr. Bush’s team did that assertively. The initial legislation expanding government power after the attacks of Sept. 11, 2001, was the “U.S.A. Patriot Act.” The warrantless eavesdropping that became so controversial was rebranded the “Terrorist Surveillance Program.” The enemy was, for a time, dubbed “Islamofascism,” until that was deemed insensitive to Muslims.

Now Mr. Obama is coming into office determined to sweep all that rhetoric away, even if he is keeping much of the policy that underlies it. Aides argue that they are not trying to spin their priorities through words, only to excise the spin applied relentlessly by the Bush administration. But they are also trying to send a clear and unmistakable message that the old order is gone.

“You have to tell the American public and the world that there’s a new sheriff in town without opening up the jail and letting all the prisoners out,” said Matt Bennett, vice president of Third Way, a moderate Democratic advocacy group. “The changing of the way they talk is a low-risk way of purging some of the Bush-era stuff without doing any damage.”

Indeed, for all the shifting words, Mr. Obama has left the bulk of Mr. Bush’s national security architecture intact so far. He has made no move to revise the Patriot Act or the eavesdropping program. He has ordered Guantánamo to be closed in a year but has not turned loose all the prisoners. The troop buildup in Afghanistan resembles the one Mr. Bush ordered in Iraq two years ago.

In cautioning against the “surge” label, Mr. Reid clearly wanted to avoid associating the Obama strategy in Afghanistan with the Bush strategy in Iraq, a strategy that both he and the president opposed at the time. The two have never repudiated their opposition to the Iraq buildup, even though many now credit it with helping to stabilize the country. And any language suggesting parallels between the two approaches could aggravate the party’s liberal base, much of which is already suspicious of committing more forces to Afghanistan.