Republican presidential candidate Donald Trump points to the crowd after speaking during a campaign event at the DoubleTree by Hilton Philadelphia Valley Forge in King of Prussia, Pa., on Tuesday November 01, 2016. (Photo by Jabin Botsford/The Washington Post)

KING OF PRUSSIA, Pa. — Republican presidential candidate Donald Trump vowed on Tuesday to summon Congress into a special session to end and replace the Affordable Care Act, as he portrayed the repeal of the contentious health-care law as a prime reason for voters to elect him.

In midday remarks in the battleground state of Pennsylvania, Trump went slightly beyond his previous promise to try to end the ACA, widely known as Obamacare, on the first day of a Trump administration. But his call for a special session puzzled many, as the current Congress is scheduled to reconvene after the election, and the new one will gavel in January, before Inauguration Day.

Trump did not, however, plow any new ground with the contours of his proposals to replace the 2010 law. He said that he would encourage Health Savings Accounts, allow insurers to sell policies across state lines and convert Medicaid from an entitlement program to a block grant to states — ideas long favored by GOP conservatives.

“People all across the country are devastated,” Trump said to a small invited audience gathered outside Philadelphia. “In many instances, their health-care costs are more than their mortgage costs or their rent, which by the way is a first in American history. This is particularly unfair to millennials and younger Americans, generally, who will be totally crushed by these massive health-care costs before they even get started on their journey through life.” He did not provide data to support his assertions.

The rare joint speech by Trump and his running mate, Indiana Gov. Mike Pence, was timed to coincide with the opening day of the fourth year's open-enrollment period for insurance marketplaces across the country created under the ACA. Obama administration officials have predicted that 13.8 million people will sign up for health plans by the time the enrollment season ends three months from now — about 1 million more than a year ago.  

Federal health officials last week announced insurance prices for 2017 that reflected what had become clear piece by piece: With some major insurance companies dropping out of ACA exchanges in many states, insurance premiums are tending to rise, and the average number of insurers selling plans to marketplace customers in their area is tending to decrease. For the 38 states relying on HealthCare.gov, the federal exchange, premium rates for the coming year are increasing, on average, by 25 percent for a significant group of midlevel “silver” plans that are the basis of federal ACA subsidies.

According to an analysis by the Health and Human Services department, most customers buying ACA coverage — intended for people who cannot get affordable health benefits through a job — will be cushioned from the effects of the rising prices by the tax credits under the law. With about 85 percent qualifying for those subsidies, more that three-fourths of ACA customers will be able to find a health plan for which they will pay no more than $100 a month in premiums.

“This year, the vast majority of consumers will qualify for tax credits that help keep coverage affordable, and it’s easier than ever to shop around and compare options,” HHS Secretary Sylvia Mathews Burwell said on Tuesday, as she spent the day giving radio and television interviews in targeted markets to draw attention to the start of the enrollment period.

That comforting portrayal contrasted markedly with the alarmist characterizations by Trump and Pence. “If we don’t repeal and replace Obamacare, we will destroy health care in America,” Trump said, saying that rescinding it “is one of the single most important reasons why we must win on Nov. 8.” Still, Trump dedicated only about five minutes to the topic in a roughly 20-minute speech.

Speaking just before the candidate at the top of the ticket, Pence said: “Families will be pummeled with unprecedented sticker shock.”

Trump also said of his opponent, Democrat Hillary Clinton, “she wants to put the government totally in charge of health care in America.” His assertion goes far beyond Clinton's position. She endorses the ACA, which relies on private insurers in the marketplaces created under the law. She wants to make a variety of changes to the statute, including allowing people 55 and older to buy into Medicare and permitting states to choose to create a government-administered alternative to private insurers in the marketplaces.

Trump said, too, that ACA insurance premiums will increase by 60 percent next year in Pennsylvania. In contrast, the HHS analysis predicts that, taking subsidies into account, 75 percent of insurers will be able to pay $100 or less for monthly premiums.

The event was held in a hotel ballroom near a mall in this town in the Philadelphia suburbs, not far from Valley Forge, the military encampment where the American Continental Army spent a painful winter during the nation's war for independence. Pence said the campaign selected the location because Valley Forge was “a turning point in the Revolutionary War.”

The event had more of a Pence vibe than a Trump one. Before the candidates arrived, soft jazz played as a few hundred guests, many of whom work in the health-care industry, mingled. Half a dozen Republican members of Congress took turns addressing the small crowd and denouncing the Affordable Care Act. Trump, who has been at odds with party leaders lately, repeatedly called on voters to elect Republicans to the House and Senate, in addition to the White House.

Goldstein reported from Washington. Sean Sullivan and Paul Kane contributed to this report.