Senate Republicans may be all over the map on an Obamacare repeal plan, but on one fundamental point — reducing insurance premiums — they are in danger of overpromising and underdelivering.

The reality is they have only a few ways to reduce Americans’ premiums: Offer consumers bigger subsidies. Allow insurers to offer skimpier coverage. Or permit insurers to charge more — usually much more — to those with pre-existing illnesses and who are older and tend to rack up the biggest bills.

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