(Newser) – The Republicans' new attempt to repeal and replace ObamaCare is suddenly in serious trouble, reports CNN, with the White House engaging in a furious push to win over wavering lawmakers. One sticking point is coverage of pre-existing conditions, with one blogger arguing that Jimmy Kimmel's emotional plea on Monday night's show may have effectively killed the GOP bill. Here's what's happening, much of which revolves around an amendment offered by Republican Tom MacArthur of New Jersey:

President Trump insists the GOP bill will cover people with pre-existing conditions in its final form. In fact, "it will be every bit as good on pre-existing conditions as ObamaCare," he told Bloomberg, echoing comments he made over the weekend.

He's basing that on the MacArthur amendment, which states explicitly that "nothing in this act shall be construed as permitting health insurance issuers to limit access to health coverage for individuals with pre-existing conditions.” (The full amendment is here.)

But that's not true, say critics, because the amendment allows states to grant waivers to insurers to set rates based on people's "health status." The New York Times explains it this way: "Rates for a person with cancer, diabetes or multiple sclerosis could be far higher than the standard rate, effectively pricing the sick out of the market without technically blocking coverage, critics say."

The American Medical Association says that "health status underwriting could effectively make coverage completely unaffordable to people with pre-existing conditions."

PolitiFact digs into the nuances and concludes that Trump's statement is "mostly false." (CNN has more particulars on the waivers.)

Politico takes note of a key GOP defector, Rep. Billy Long of Missouri. He's voting no, explaining that he thinks coverage of pre-existing conditions is one of the few things ObamaCare got right. "The MacArthur amendment strips away any guarantee that pre-existing conditions would be covered and affordable."

Defenders of the waivers say they give states necessary flexibility that will result in lower rates. "People with pre-existing conditions today can’t access health care because the premiums and deductibles are so high," says Rep. Richard Hudson of North Carolina, per the Wall Street Journal. A National Review columnist also backs them.

The vote count is razor-thin at the moment, and Margaret Hartmann at New York suggests that Kimmel's monologue may have doomed the GOP bill. Kimmel spoke of his infant's heart condition and the need for insurance to be available to people with pre-existing conditions, and he urged people to make sure lawmakers know that. He's got an audience of 2 million, and the clip is going viral. "What wavering House Republican is going to decide now is the time to come out in favor of the bill?" she writes.

(Read more pre-existing condition stories.)