WASHINGTON – The White House is mounting a stinging, sustained broadside against health insurance rate increases as President Obama and his aides enter what they hope will be the final stretch of a yearlong political war over health care reform.

Obama and his health secretary staged a two-pronged attack Monday in a stern letter to health insurance chief executives and a speech in the Philadelphia suburb of Glenside in which the president castigated insurance companies 22 times.

“How much higher do premiums have to rise,” he asked, “before we do something about it?”

The messages are part of a new strategy by Obama and those around him to ratchet up the pace and populist appeal of their rhetoric against the health insurance industry.

The barbed tone moves far beyond that of the 2008 presidential campaign, when Obama began to say that medical coverage should be accessible and affordable for more Americans.

It remains unclear whether the strategy, coming this late in the debate, will mobilize support among the public and on Capitol Hill for the legislation that the White House and congressional Democrats favor.

Obama has asked Congress to conduct final votes on the proposal within 10 days, before lawmakers leave for a two-week break.

Democratic congressional leaders are struggling to secure enough votes within their party; Republicans are calling for the proposal to be abandoned, saying most Americans oppose it.

The near-daily demonization of the insurance industry is an attempt by the White House to play to Americans’ anxieties about the health care system — and the prospect of changing it.

Polls consistently show that most people fear that the legislation would make their treatment more expensive.

By focusing on escalating insurance rates, especially for the sliver of the market in which people buy health coverage individually, the administration is emphasizing that costs will increase if Congress does not act.

“Part of the motivating factor here is letting members of Congress know there’s a price to pay for failure,” White House Chief of Staff Rahm Emanuel said Monday. “And for the public, it’s important to remind them that there are premium increases of 40 percent for as far as you can see if nothing is done.”

Emanuel’s figure referred to a recent move by Anthem Blue Cross of California to raise premiums by 39 percent for people who buy individual policies.

As the White House has launched its last-minute public relations blitz for health care reform, “there could have been no greater gift” than Anthem’s rate increase, which it has since postponed, said Drew Altman, president of the Henry J. Kaiser Family Foundation, a nonpartisan health policy and research organization.

The Obama administration, Altman said, is “trying to connect better with average people” in terms more concrete than the president used earlier in the debate when he spoke about “bending the curve” of escalating health care costs and curbing future budget deficits.

Republicans doubt the rhetoric will work. Linda DiVall, a GOP strategist, said White House officials “are trying to disguise their vulnerability” that Democrats’ approach would not control costs “by hiding behind a greater villain” — insurance companies.

Last year, premiums for employer-sponsored insurance rose by an average of 5 percent, while inflation fell by nearly 1 percent, according to Kaiser. Over the previous decade, premiums went up by 131 percent, compared with 28 percent for inflation.

The administration says the rate increases reflect excessive industry profits; insurance lobbyists counter that their rates mirror underlying increases in prices charged by doctors, hospitals and drug companies.

America’s Health Insurance Plans, the industry’s main lobby, plans to spend more than $1 million on a nationwide advertising campaign this week to, as one official with the group said, “set the record straight about rising health care costs.”

Broad majorities of insured Americans say they are satisfied with their coverage, according to Washington Post-ABC News polls. Only one in eight say insurance would improve if the health care system were changed.

But that relative satisfaction coexists with anxiety.

More detailed Kaiser surveys show that two-thirds of insured people say they worry that their insurance or their care will become more expensive — and nearly half say they have delayed or skipped care because of the cost.