Sen. chief rival for the Democratic presidential nomination, Sen. , often tiptoes in his attacks on her, sometimes criticizing her record without using her name.
But the leading Republicans are running as if Clinton were their opponent, constantly invoking her as a way to pep up disconsolate conservatives and as a reminder of the stakes in an election for which the rank-and-file GOP has no enthusiasm.
"Did you hear what Hillary Clinton said about the economy, by the way?" former Massachusetts Gov.asked at an event Friday night, doing his best Jay Leno.
"She said, you know, America has always been an on-your-own society. … But she said it's time to change that. [Audience laughter.] She said we need to become a shared-responsibility society, a we're-all-in-it-together society. So for her, it's out with Adam Smith and in with Karl Marx!"
The audience dissolved in extended whoops, cheers and applause. Romney, speaking to the inaugural "Defending the American Dream Summit" of the free-enterprise group Americans for Prosperity, could see he had a hit on his hands.
"Someone just sent me an e-mail the other day," Romney continued. "It said: You know, when Hillary Clinton thinks 'private sector,' she thinks that's a new recruit in the Army."
He's got a million of 'em. "She doesn't have a lot of experience in the private sector," Romney said. "Have you heard her latest brainstorm? … That is the idea of giving every child born in this country a $5,000 bond without regards to whether they were in a wedlock setting, or without regards to the fact that the $5,000 bond gets paid for by borrowing $5,000 from the very child's future."
That drew chuckles and, eventually applause and chants.
Then the big finish: "In my opinion, Hillary Clinton couldn't get elected president of France, let alone president of the United States."
Romney was showered with applause. "Wow! What a crowd!" he said delightedly. "Now all this would be kinda funny, to tell you the truth, if it weren't so important, so critical."
Therein lies the reason Clinton - often invoked simply by her first name - provides such a handy foil for beleaguered Republicans. It gives them a target at a time when their own party is widely blamed for mismanaging the Iraq war, the federal budget and the levers of government.
It allows the hopefuls to abide nominally by President Ronald Reagan's "11th commandment" against speaking ill of a fellow Republican.
And perhaps most importantly, it helps Republican candidates make the case that they are not afraid to take on Clinton in a year when the party is desperate to win and campaigns are making their candidate's electability a central argument.
Former New York Mayor, speaking to the free-enterprise summit Friday morning, also jested about the "baby bonds" idea Clinton had mentioned in an address to a Congressional Black Caucus town hall meeting.
"Hillary Clinton, the other day, proposed giving every single baby born in the United States [laughter] a Hillary bond [laughter] worth $5,000 each. Now, I know this never occurs to the - people like Hillary and the other Democrats here in Washington, but you know something? I got news for you, this costs money. [Laughter.] It doesn't come from the trees, it doesn't come down from heaven."
Giuliani, who has said he expects Clinton to be the Democratic nominee, often sounds like he's already in a general election. When he walked out of a diner in Manchester, N.H., last week, he walked up to the clutch of television cameras and started lashing out at Clinton.
On Friday, he said, "Excuse me if I don't think that hundres of millions of Americans can figure out the common good better than Hillary Clinton or the bureaucrats."
Amid the cheers and applause, an audience member shouted, "Amen!"
In the service of a punch line, Giuliani even inaugurated her: "When our medicine becomes socialized under Hillary Clinton, just where are the Canadians going to go for their health care?"
A third Republican presidential candidate, former Arkansas Gov., used the free-enterprise summit to bash Clinton - this time by giving a cartoonish description of her health plan, which allows a choice of public or private coverage and requires insurers to offer coverage to anyone who applies and pays their premium.
"Hillary says, let's give everybody a card and they can have all the health care they want," Huckabee said. "Can you imagine if we did that with groceries? Giving every American a grocery card, you could go to the store and shop and put anything and everything in your basket that you wanted, and you wouldn't have to pay for it. Somebody else would pick up the tab. Can you imagine what kind of grocery expenses we would have?"
Come to think of it, can you imagine what the Republican candidates would say on the stump if they didn't have Hillary Clinton?