Running against Trump's often outlandish behavior will be tempting, but it's a losing strategy as voters are prone to dismiss Trump's antics as entertainment, said David Beattie, a Democratic pollster. Clinton instead must find a narrow, narrative argument to make against Trump, said Beattie, who worked for Democrats in the 2010 and 2012 Connecticut Senate races against Republican Linda McMahon, a multi-millionaire former president of the WWE, or World Wrestling Entertainment.
In Connecticut, voters weren't interested in salacious details from McMahon's past, such naming her yacht "Sexy Bitch" or, in the wrestling arena, degrading a woman portraying her husband's mistress by ordering her to undress, crawl around the ring, and "bark like a dog."
Instead, Beattie said, McMahon's opponents honed in on comments made during the campaign, such as her support for phasing out Social Security. "I've run a lot races against candidate who have said crazy things, and those crazy things seem to have less and less impact," Beattie said in an interview.
"With Trump, the hardest thing is knowing where to attack," Beattie said. "He says so much and changes so frequently, it's almost like you're always behind, because you don't know what he's going to say. You have to have a narrative: He's not a deal-maker. He's a bad businessman who's taken advantage of the system to enrich himself, and he's not interested in helping people."
So far, Clinton and her allies have taken an all-of-the-above approach. News releases from the campaign have referred to Trump as "unpredictable" and "risky," while highlighting his changing positions. The Democratic National Committee is aping Trump's name-calling, referring to the presumptive nominee as "Dangerous Donald." Correct the Record, a pro-Clinton super-PAC, e-mailed reporters on Friday, "DONALD DUCKS ON RELEASING HIS TAXES. What a Quack."
"The Republicans who tried to change their tone and match him, every one lost," Beattie said. "And that's going to happen to the Democrats in the fall if they try to do that, too. Because Donald does this naturally."
David Axelrod, a top strategist in Barack Obama's two presidential victories, said Trump's shifting positions raise questions about how he would perform in the world's most powerful political job.
"The question with Trump, at the end of the day, is not his positions but his temperament," Axlerod told Bloomberg Politics. He said Trump's multiple positions on a single issue "raise concerns about his suitability for a job in which sobriety, consistency and reliability are absolutely required."
There was a time in American politics, in the not-too-distant past, when voters held presidential candidates responsible for their promises.
"Read my lips," George H.W. Bush said at the 1988 Republican national convention while accepting his party's presidential nomination. "No new taxes." When President Bush later negotiated a budget with Democrats that included a tax increase, it became a point of attack from Democrat Bill Clinton, Hillary's husband, who beat Bush in 1992.
But while Bush was punished for negotiating away a campaign promise -- in his case while dealing with a Congress controlled by Democrats to keep the government running -- Trump is openly saying he'll do just that.
"I'm not softening my stance at all," Trump said Friday on NBC, when asked whether he was backtracking on a plan to ban Muslims from entering the U.S. "But I'm always flexible on issues. I'm totally flexible on very, very many issues." The immigration plan, announced in a press release on Dec 7, was "just a suggestion," he said.
Trump is navigating unchartered political waters there. If policy proposals are the ballast of a traditional campaign, Trump is throwing it overboard and betting that a minimalist approach to policy will lighten the load and keep his candidacy from sinking.
The candidate, for example, promised to release his tax returns, as presidential nominees have done for the past four decades. The delay, he has said, has to do with an audit by U.S. authorities. But when asked on May 13 about his tax rate, he bristled. "None of your business," Trump said on ABC's "Good Morning America" when asked to disclose his income tax bracket.
After suggesting that the U.S. could intentionally default on its debt -- "I would borrow, knowing that if the economy crashed, you could make a deal," he said on CNBC on May 6, declaring himself "the king of debt" -- Trump made an about-face. On May 9 he declared American immunity to default: "You never have to default because you print the money," Trump said in an interview on CNN's "New Day."
And after bragging about a plan during the primary campaign to cut taxes wider and more deeply than any of his competitors, Trump now says he'd be willing to raise rates on the wealthy. "It's not a policy," Trump said on Fox News on May 12 when asked about his willingness to negotiate the tax plan. "It's not anything. It's a proposal."
Benenson said the Clinton campaign will remind voters of Trump's initial positions, the ones he used to build support and vanquish his primary opponents. "Everybody has heard it, everybody knows it," he said of Trump's policies. "He cannot airbrush his campaign. He's can't airbrush his insulting comments. He's been running for president for over a year, and America has heard everything he's had to say."
Rarely has a presidential nominee rushed so quickly to water down key ingredients of a successful primary campaign. But rarely has there been a party standard-bearer like Trump.
"Stylistically, where Trump has shown a great deal of talent has been his ability to realize when the push-back was hitting critical mass," said Ed Goeas, a Republican pollster.
Trump's strategy in the primary race was to "say something else crazy to change the subject," Goeas said. "But he's in a situation now in the general election," he added, "where he can't quite do that anymore."