As it quickly became apparent, she had come to talk about Barack Obama.

“There is one job we can’t afford on-the-job training for,” said Mrs. Clinton, standing in a gym in front of a sign that said “Rebuilding the Road to the Middle Class.” “That is the job of our next president. That could be the costliest job training in history.”

She added, “Every day spent learning the ropes is another day of rising costs, mounting deficits and growing anxiety for our families. And they cannot afford to keep waiting.”

Mrs. Clinton’s latest sweep through Nevada and Iowa marked a sharp turn onto the offensive for her and her campaign, and she’s clearly warmed to the role. Starting with her preemptively truculent debate performance last week and continuing in a series of appearances, the campaign has chosen to alter a dynamic that had her as a passive front-runner weathering daily attacks from her rivals.

Meanwhile, her opponents have taken to talking about her in terms normally reserved for the likes of Karl Rove.

“She of all people, having complained so often about ‘the politics of personal destruction,’ should move quickly to either stand by or renounce these tactics,” Mr. Obama said on Nov. 17 in response to a Bob Novak column saying “agents” of the Clinton campaign had clandestinely claimed to have dirt on Mr. Obama. “The cause of change in this country will not be deterred or sidetracked by the old ‘Swift Boat’ politics.”

(The Clinton campaign swiftly denied the Novak column and said that the younger Mr. Obama had fallen into a trap.)

And the next day, on Nov. 18, John Edwards’ communications director Chris Kofini accused the Clinton campaign of purposefully misconstruing Mr. Edwards’ statements on health care. “Manipulating words and lying about them is a tool right out of the Republican playbook,” he said in a statement. “As Democrats, we shouldn’t stoop to that level.”

Mrs. Clinton’s supporters, needless to say, see the high-pitched counterattacks as a sign of desperation.

“Tactically, Hillary is the most sure-footed,” said Fred Hochberg a prominent Clinton donor who spent part of last week building support for Clinton in Iowa. “She’s running a disciplined campaign and people will use any tactic to try and take down the front-runner.”

Another major fund-raiser for Mrs. Clinton, Robert Zimmerman, sees the Republican references as her rivals’ way of trying to scare up Democratic support with just over 40 days before the Iowa caucus.

“That’s the first warning sign of how desperate they are getting,” said Mr. Zimmerman, a public relations marketing executive. “No one has faced more attacks from Republicans than Hillary Clinton. Democrats are not going to accept any comparisons between her and Republicans.”

Interestingly, a Washington Post-ABC News poll released on Nov. 19 showed her narrow lead in Iowa having vanished, with Mr. Obama at 30 percent, Mrs. Clinton at 26 percent and Mr. Edwards at 22 percent.

While those results are within the margin of error, nearly twice as many people found Mr. Obama more honest and trustworthy than Mrs. Clinton, and Mr. Obama’s emphasis on change resonated with more Democrats as a top priority than Mrs. Clinton’s stressing of experience.

During her policy address in Knoxville, Mrs. Clinton seemed to be promising the best of both worlds, pledging to reverse the economic policies of the current administration, but doing so in a way that distinctly echoed the previous one.

“They [Republican candidates] see $9 trillion in debt and say, ‘Why not trillions more?’” she said. “They see tax cuts for wealthy Americans and big corporations and say, ‘Why not more?’ They see one attempt to privatize Social Security and say, ‘Why not one more?’ In short, they see eight years of Bush economics and say, ‘Why not eight more?’

“Well, here’s my response to that: You’ve got until January 20, 2009. And not one day more will we put up with these failed policies.”

In campaign stops throughout Iowa on Nov. 19 and 20, Mrs. Clinton delivered more of the same.

At an elementary school in Vinton, Mrs. Clinton told a crowd of enthusiastic Clinton supporters, “It took one Clinton to clean up after Bush, and it will probably take another.”

And at an evening event at the Bluegrass Cafe in Tama, where the album covers of Sammy Hagar, ZZ Top and Bob Seger hung on a wall above Clinton’s “Turn Up the Heat” campaign posters, she sounded almost angry when she said, “Everywhere you look, the economic polices of George Bush have been bad for the middle class. There is no way to get around it.”

When asked about the sharply divided American public, she responded, “I think history will judge George Bush very harshly, because he pursued a divisive political agenda instead of a unifying political agenda. He was more interested in scoring partisan points than pulling us together as a nation.”

She argued that she had made peace with many of her old Republican enemies.

“I am looking for away to isolate the negativity,” she said. “To diminish the extreme political positions. America is not a country of extremism; we’re centrists.”

But seconds later, she showed a flash of the ruthlessness her Democratic rivals have been complaining about.

“We can surround them and we can defeat them,” she said of [enemy] special interest groups. “And we can isolate, and we can marginalize them, because they have been after me for 15 years, and I’m still here, and I’m still standing.”

Perhaps her sharpest attack of all came on the afternoon of Tuesday, Nov. 20, at an event she didn’t even show up for. Supporters had packed into a firehouse in Shenandoah to hear Mrs. Clinton speak, but her plane was stuck at an airport in Omaha, where she had been diverted because of fog.

After a while, people started to file out, but Mrs. Clinton did eventually manage to address the remaining attendees by speakerphone. She began with some standard pleasantries, discussed a proposal to safeguard America’s food supply and then segued, rather abruptly, into the subject of experience.

“Now voters will judge whether living in a foreign country at the age of 10 prepares one to face the big complex international challenges the next president will face,” she said, in an unmistakable reference to the unusually cosmopolitan upbringing of Mr. Obama, which he recently cited as a source of foreign policy expertise. “I think we need a president with more experience than that.”