US Polls Donald Trump Tremors and Hillary Clinton early Struggles unnerve her Campaign 

Democrats could hardly believe their good fortune last month when it became clear that Hillary Clinton was headed to a general election showdown with Donald J. Trump. Mr. Trump carried so much baggage and had insulted so many voting blocs that some Clinton supporters began to imagine a landslide.

But early optimism that this would be an easy race is evaporating. In the corridors of Congress, on airplane shuttles between New York and Washington, at donor gatherings and on conference calls, anxiety is spreading through the Democratic Party that Mrs. Clinton is struggling to find her footing.

While she enjoys many demographic advantages heading into the fall, key Democrats say they are growing worried that her campaign has not determined how to combat her unpredictable, often wily Republican rival, to whom criticism seldom sticks and rules of decorum seem not to apply.

Mrs. Clinton is pressing ahead with a conventional campaign, echoing the 2012 themes used against the Republican nominee that year, Mitt Romney. But Mr. Trump is running a jarringly different crusade: accusing her husband, former President Bill Clinton, of rape; proposing that the country conduct brutal methods of torture; and suggesting that South Korea and Japan be permitted to develop nuclear arms. Prominent Democrats say a more provocative approach is needed.

“The guy’s a maniac,” John Burton, the chairman of the California Democratic Party, said about Mr. Trump. Referring to a famous 1964 political message, he said, “You could run the old L.B.J. ad against Goldwater, with ‘Three, two, one,’ and a hydrogen bomb blows up with a little girl counting daisies.”

Of course, Mr. Trump faces many hurdles himself, and has stumbled in managing his growing campaign as he shifts toward a general election. But Democrats suggest that the past few weeks have shown that Mrs. Clinton and her aides must become more agile and creative against him.

The sense of nervousness crystallized this week when Mrs. Clinton devoted campaign events across California to hitting Mr. Trump for not releasing his tax returns and depicting him as a cold corporate titan who profited off the housing crisis. Such charges helped undermine Mr. Romney four years ago. Yet Mrs. Clinton’s remarks received little in-depth coverage in the news media, while cable channels went live with Mr. Trump’s rat-a-tat recitation of “Crooked Hillary,” his favored nickname for her.

Ken Salazar, the former Colorado senator who has been mentioned as a possible Clinton running mate, said the campaign should draw a sharp contrast between Mr. Trump’s shortcomings and Mrs. Clinton’s potential to be “the most quali by TNT,