NEW YORK — With Election Day less than two months away, Democrats are increasingly worried that Hillary Clinton has not built a formidable lead against Donald Trump despite his historic weaknesses as a national party candidate.

Even the Democratic nominee’s advisers acknowledge that she must make changes, and quickly. Clinton leads Trump by a mere 3 percentage points, having fallen from her high of 9 points in August, according to the latest RealClearPolitics average.

That tightening has frustrated many Clinton allies and operatives, who are astonished that she isn’t running away with this race given Trump’s deep unpopularity and never-ending stream of controversial comments.

“Generally, I’m concerned, frankly,” said former Democratic Senate leader Thomas Daschle of South Dakota. “It still looks positive, and I think if you look at the swing states and where she is right now, she’s got a lead. But it’s certainly not in the bag. We have two months to go, and I think it’s going to be a competitive race all the way through. I would say she’s got at least a 60 percent chance of winning.”

At the same time, Daschle said, “all the things that Trump has done, the numbers should be far more explicitly in her favor, but they’re not.”

Among Democrats’ concerns is the fact that Clinton spent a great deal of time over the summer raising millions of dollars in private fundraisers – while Trump was devoting much of his schedule to rallies, speeches and TV appearances.

Clinton has focused more heavily on fundraising than Democratic strategists had hoped would be necessary at this stage, partly to help Democrats running for Congress and state offices who would be useful to Clinton if she is president and partly to hold off further erosion in the polls.

A goal for Clinton now, aides said, is to spend more time trying to connect directly with voters by sharing a more personal side of herself – and by telling them where she wants to take the country.

Trump’s campaign, meanwhile, battling historic unpopularity and a flood of public Republican defections, has been delighted and somewhat relieved to see the polls tighten. Aides attributed the change to Trump’s packed August schedule, including a visit to Mexico, as well as increased discipline.

Just as Trump was repeatedly underestimated during the Republican primaries, his aides say he is again being underestimated heading into the general election. There’s a sense in the campaign that things are finally coming together and that Trump can propel himself ahead of Clinton over the next two months.