The ACA was a repackaging of Massachusetts' "RomneyCare" that was passed by Republicans in that state. The reason this legislature was chosen was because it was thought to be a bipartisan solution to rising healthcare costs.
FYI RomneyCare was passed by a supermajority of Democrats in the MA state legislature. They negotiated some parts with Governor Romney but the reform was not a “republican idea”. ObamaCare in general was not a republican plan - it was a moderate Democrat plan.
People at conservative think tanks coming up with an idea doesn’t make it “republican”. In reality the party ignores many things that the heritage foundation or various other foundations or think tanks say, they’re much more focused on politics than on ideas.
https://en.m.wikipedia.org/wiki/Massachusetts_health_care_re...
And if we skip ahead 4 years to 1993, a Republican Senator introduced, a bill with 20 Republican co-sponsors including Bob Dole, Orrin Hatch, and Charles Grassley called the HEART bill.
That bill included an individual mandate, vouchers for low income individuals, and protection for prexisting conditions.
Not all Republicans supported this plan, but almost half of the Republican Senators including most of the leadership supported it. I'd call that a Republican plan--a plan based squarely on the proposal from the heritage foundation.