Sen. Hillary Rodham Clinton doesn't tell Iowa voters that in his younger days, her chief rival for the Democratic nomination behaved badly. She never lays out incidents from Sen. Barack Obama's past that could be exploited in a general election contest; doing so might be considered an unseemly personal attack.
But with the Iowa caucuses just two weeks away, she is sidling up to that fine line -- and, in some cases, her campaign surrogates are fleshing out what the candidate leaves unsaid.
Nominating Obama would be a gamble, the senator from New York is suggesting to crowds. Republicans would surely and swiftly make him a target.
Speaking at an antique-car museum here the other day, Clinton said that a major consideration should be which Democratic candidate is most likely to withstand the looming Republican attack and win in 2008.
Recent polling shows that Obama would be competitive in the general election; a USA Today-Gallup poll showed that he fares a bit better than Clinton in head-to-head contests with three top Republicans.
But Clinton's message is that once the GOP finishes sullying him, he won't look so pristine. In contrast, she is, she said, "ready and able to run a campaign against whatever" -- a word she emphasized -- "the Republicans decide to throw our way."
In addressing voters, she does not specify what "whatever" might encompass, nor does she mention Obama by name. But some of her surrogates have.
During a recent newspaper interview, her New Hampshire campaign co-chairman invoked Obama's teenage drug use, which the senator from Illinois has publicly discussed. Such indiscretions, said Bill Shaheen, could make Obama vulnerable.
"It'll be, 'When was the last time? Did you ever give drugs to anyone? Did you sell them to anyone?' " Shaheen said.
Clinton's campaign repudiated the remarks, and Shaheen quickly resigned. But there have been other cases of Clinton aides and loyalists zeroing in on aspects of Obama's history that she won't publicly mention.
In a television appearance, her top strategist, Mark Penn, used the word "cocaine" in talking about the Shaheen episode. An advisor to another campaign jumped in and chided Penn for making a gratuitous reference.
Former Sen. Bob Kerrey (D-Neb.), who endorsed Clinton on Sunday, later gave an interview where he mentioned Obama's middle name -- "Hussein," a family name -- and added that Obama's Kenyan father and paternal grandmother were Muslim (the candidate is Christian).
Kerrey has said that he was merely trying to compliment Obama, casting him as a worldly figure -- but his words could also serve to agitate voters.
"In theory," said Bill Clinton, who faced similar criticism when he ran for president as the 45-year-old governor of a small Southern state, "we could find someone who is a gifted television commentator and let them run."
Obama goes after Sen. Clinton in a different fashion. He has accused her of equivocating on policy positions. He has also voiced doubts that she would bring about real change, dismissing a Hillary Clinton presidency as "Bush-Cheney lite."
Campaigning in New Hampshire on Wednesday, he mocked Clinton -- without mentioning her by name -- for refusing to act without "poll-testing" the consequences, and he suggested that she wants the presidency for the wrong reasons.
"I'm not running because I think this is owed to me, because I think it's my turn," he said.
With so little time before the first contests, Clinton is making what advisors call her closing argument. She invokes her battles with Republicans dating to the early 1990s as testament to her staying power.
"The Republicans won't give up without a fight, will they?" she said earlier this month in Winterset. "They're not going to say, 'we messed it up; we should just be ashamed of ourselves and leave.' They're going to launch their political attacks. I think I'm the best, most tested person to withstand that, having survived it now for 15 years."
There are voters who find this persuasive. A new Field Poll survey of California voters showed that Democrats indeed believe Clinton to be more likely to prevail over the Republicans.
But the other leading Democratic candidates reject that argument. A spokesman for Obama predicted Wednesday that if Clinton is the nominee, she could win only by the slimmest of margins. The thinking behind that view is Clinton is a partisan figure who will drive away Republican and independent voters.
A spokeswoman for John Edwards' presidential campaign said the former North Carolina senator can appeal to Southern voters in ways that the other contenders cannot.
Obama did not directly address the continuing remarks from the Clinton camp during his events Wednesday in Manchester and Concord, N.H. But Ric Hopkins, a 53-year-old undecided voter who said he was still considering the entire Democratic field, as well as long-shot GOP candidate Rep. Ron Paul, said the Clinton campaign's recent attacks on Obama's experience were upsetting and could backfire in New Hampshire.
"They're trying to hang this inexperience -- 'you're rolling the dice, he's a greenhorn, he doesn't know what he's doing' thing on him -- but I think that's a cheap shot. Negativity does not play well."
Times staff writer Maeve Reston in New Hampshire contributed to this report.