Politifact rated the statement "PANTS ON FIRE" on October 5th, 2018.
Prior to the Politifact article, it was hard to believe that the statement could be true, as many websites are reporting the exact opposite.
Politico, The New York Times, and many others are reporting on the ads that Democratic House and Senate candidates are running in their districts.
Democratic candidates are getting very personal on the campaign trail as they push to preserve Obamacare, frankly sharing tales of their own health struggles.
In a House district in Illinois, registered nurse Lauren Underwood talks about a heart condition that would put her at risk for losing her health coverage if Congress or federal courts strike down the Affordable Care Act and its protections for people with pre-existing conditions. In California’s Central Valley, T.J. Cox tells voters that before Obamacare, his insurance refused to cover his wife’s C-section because it considered her pregnancy a pre-existing condition. And in suburban Detroit, Elissa Slotkin’s brutal television ads includes footage of her mother as a dying cancer patient who for years had been denied insurance.
The New York Times
This cycle, even Democrats running in red states are unapologetically putting health care at the center of their campaign messages. There’s a reason: Republican efforts to overhaul the health care system last year were deeply unpopular.
A lawsuit brought by several states imperils the health law’s protections for people with pre-existing health conditions, the law’s most popular provision. Recent polls show growing numbers of Americans rank health care as a top issue, and coverage for pre-existing conditions as an important policy.
Regardless of source, Democrats are campaigning on Republicans threatening to remove pre-existing condition protection, which is deeply unpopular in the country.
Politifact finally covered the statement in an 5 October 2018 piece entitled
Donald Trump's Pants on Fire claim about Democrats, pre-existing conditions. Some of the relevant portions are copy-pasted below.
"We will always protect Americans with pre-existing conditions," Trump said around the 34:00 mark. "We’re going to take care of them. Some of the Democrats have been talking about ending pre-existing conditions. And some people have -- you know what I say? We'll get a little more money from China. It'll be just fine. It'll be just fine. We'll be just fine."
This seems to match OP's transcription in the question.
Politifact gets into the meat of the article.
Is he right that "some of the Democrats have been talking about ending pre-existing conditions"?
We found zero evidence of this.
For starters, Trump’s assertion is illogical given the Democrats’ role in passing the law and Democratic efforts to hammer Republican candidates over pre-existing condition protections on the campaign trail.
Politifact provides the following campaign ads of Democratic candidates to back this up, showing attempts by Democratic senators to protect pre-existing conditions.
Politifact also talked to the spokesman for House Minority Leader Nancy Pelosi, and received a response saying that nothing similar to what President Trump claimed has been talked about by Democrats.
Drew Hammill, a spokesman for House Minority Leader Nancy Pelosi, D-Calif., said there is no such chatter among Democratic officeholders or candidates.
The article concludes with this line.
The White House did not reply to an inquiry seeking examples. Neither did the office of the Senate majority leader or the House speaker.