Progressives have already homed in on Republican efforts to privatize Medicare as one of the major domestic political battles of 2017. If Donald J. Trump decides to gut the basic guarantee of Medicare and revamp its structure so that it hurts older and sicker people, Democrats must and will push back hard. But if Democrats focus too much of their attention on Medicare, they may inadvertently assist the quieter war on Medicaid — one that could deny health benefits to millions of children, seniors, working families and people with disabilities.

Of the two battles, the Republican effort to dismantle Medicaid is more certain. Neither Mr. Trump nor Senate Republicans may have the stomach to fully own the political risks of Medicare privatization. But not only have Speaker Paul D. Ryan and Tom Price, Mr. Trump’s choice for secretary of health and human services, made proposals to deeply cut Medicaid through arbitrary block grants or “per capita caps,” during the campaign, Mr. Trump has also proposed block grants.

If Mr. Trump chooses to oppose his party’s Medicare proposals while pushing unprecedented cuts to older people and working families in other vital safety-net programs, it would play into what seems to be an emerging strategy of his: to publicly fight a few select or symbolic populist battles in order to mask an overall economic and fiscal strategy that showers benefits on the most well-off at the expense of tens of millions of Americans.

Without an intense focus by progressives on the widespread benefits of Medicaid and its efficiency, it will be too easy for Mr. Trump to market the false notion that Medicaid is a bloated, wasteful program and that such financing caps are means simply to give states more flexibility while “slowing growth.” Medicaid’s actual spending per beneficiary has, on average, grown about 3 percentage points less each year than it has for those with private health insurance, according to the Center on Budget and Policy Priorities — a long-term trend that is projected to continue. The arbitrary spending caps proposed by Mr. Price and Mr. Ryan would cut Medicaid to the bone, leaving no alternative for states but to impose harsh cuts in benefits and coverage.