Republicans are expected to score gains in 2014 because of their advantage among older voters, the voters most likely to turn out in midterm elections. That advantage has appeared surprisingly recently—and there is reason to think it won’t last long.

In 1988, voters older than 60 were the age group least likely to vote for George H.W. Bush over Michael Dukakis. The disparity was not huge: Bush would still have won even if the only votes counted had been cast by those older than 60. But it’s still suggestive that Bush ran strongest among the “Silent Generation” cohort just slightly too young to remember the Depression and World War II—and that he performed worst among those who personally remembered the New Deal, who had been of age to benefit from the G.I. Bill, and who now received Social Security and Medicare.

In the presidential election of 2000, Al Gore won 51 percent of the vote among those older than 65. Each younger cohort was incrementally less likely to vote for him. He did worst among those 18 to 24, who broke 47 percent for Gore, 47 percent for Bush and 5 percent for Ralph Nader.

The emergence of the older voters as a massively solid Republican bloc is a post-Obama phenomenon.

The Pew survey explained the trend in a 2011 report. The Silent Generation that voted for Bush in 1988 had retained its conservatism into its retirement years. No news there. The news was among the next cohort, the Baby Boomers: After the year 2000, the Woodstock generation veered abruptly to the right.

In their youth, the Boomers had expressed strongly liberal views about the role of government. In 1989, asked to choose between a bigger government that did more for people versus a smaller government that did less, they opted for bigger government by a margin of 52-40. By 2007, that preference had reversed itself, 52-35, and it has remained reversed through the Obama years. Even more striking was the collapse in trust in government among the Boomers: In 1997, 38 percent of them trusted the government to do the right thing most of the time; by 2009, only 16 percent did so, the same suspicious percentage as their formerly more conservative “silent” elders.

These trends explain the present. But they don’t predict the future.

As human life extends, it no longer makes sense to think of 65 as “old age.” We live in the age of the 65-year-old marathon runner, the 65-year-old rock star, and the 65-year-old new father. (At today’s pace of technological improvement, we may soon be surrounded by 65-year-old new mothers.)

Old age comes later now. But when it comes, it changes people in the same way it always did. Women begin radically to outnumber men. (In 2010, the older-than-80 population included 4 million males and 7.2 million females). Personal savings are exhausted. (Average net worth drops by 25 percent between age 65 and age 75.) Dependency rises. Attitudes to government change.

The older you get, the more you appreciate Social Security and Medicare …

... and the more you mistrust proposals for reform that might affect current recipients. In 2009, 43 percent of people in their twenties were open to reforms in entitlements that might touch those now receiving Social Security and Medicare; only 27 percent of people in the strongly conservative groups older than 65 would consider it.

As yet, few published surveys break out the differences between people in their sixties and eighties. Working politicians notice it, though. As one very successful political operative told me, “The No. 1 concern of every voter over 80 is, ‘Will my check arrive on time?'”

Cultural conservatism appeals strongly to the elderly. The bold economic individualism espoused by so many in the Republican Party since 2009? Not so much. A 501(c)4 group closely connected to GOP leaders and donors conducted a series of focus groups in spring 2012 among older independents in Michigan and Florida, two states Mitt Romney hoped to win. These voters strongly endorsed the entitlements status quo and opposed any changes that would affect them personally. They refused to believe that Medicare caused deficits. (They blamed “wars” instead.)

There will soon be a lot more people digging in against benefits changes. The elderly population is poised to grow hugely quickly; the oldest of the old to grow faster still. Between 2000 and 2010, the total population grew 9.7 percent; the population older than 65, by 15.1 percent; the population older than 80, by 23 percent. That last group now numbers more than 11.2 million—and demographers expect it to grow even faster over the decades ahead.

Here’s at least one obvious way this change will affect older voters. Among all voters 65-plus, women outnumber men only slightly: In 2010, for every 100 women older than 65, the Census counted 95.5 men. The political result? The mild preference in favor of President Obama among older women voters was swamped by the intense hostility of older men.

As we advance from age cohort to age cohort, however, the men dwindle away. At 75, the Census counts 80.2 men for every 100 women; at 85, 58.3 men for every 100 women. The good news for men: Our survival prospects are rising! In 1990, the Census counted only 45.6 men for every 100 women older than 85. The bad news for the Republicans: The disparity in sex-survival rates has huge political effects on the way the old vote.

In 2010, the old as a group voted Republican because the lopsided hostility toward Obama among older men could overwhelm the mild preference for the president among older women. As the population ages, however, the ratio of men to women within the over-65 population should drop. The share of over-80s in the population is rising faster than men’s likelihood of surviving to 80. The changing sex ratio will sway the political outlook of the whole group.

Rutgers University’s Center for American Women and Politics has detailed in surveys women’s rejection of the politics of economic individualism.

Do government programs for the poor help put people on their feet—or lead to dependency for life? Men condemn such programs for inducing dependency 49-44. Women applaud them for setting people on their feet, 60-36.

What do you think is the bigger problem: unfairness in the economy favoring the wealthy, or overregulation that interferes with the free market? Men worry more about overregulation, 49-42. Women worry more about unfairness, 54-35.

When it comes to balancing the budget, 57 percent of men wish to rely principally on cutting programs. Only 50 percent of women agree. Only 22 percent of men wish to rely principally on tax increases, versus 29 percent of women.

This gap in values produces a large gap in voting—a gap that manifests itself at every age.

As the old become older, they become more female. As they become more female, they become more supportive of government’s social-welfare role—and thus more strongly Democratic.

Hazarding long-term political predictions usually ends in embarrassment. Notwithstanding, here goes:

Two decades from now, the United States likely will have a party that appeals strongly to the surging numbers of old people.

Two decades from now, the United States possibly may have a party of low taxes and fiscal austerity.

If so, they won’t be the same party.

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