Last week’s Reagan-Bush comparisons emphasized the similarities between the two presidents. But the biggest contemporary change in American politics is revealed by the difference between them. Whereas Ronald Reagan promised in his first inaugural address “to curb the size and influence of the federal establishment,” George W. Bush has no such ambition. He has expanded the Education Department that Reagan threatened to eliminate; he has created a vast new prescription drug entitlement; he has proposed a $1.5 billion government program to promote marriage. When even a self-conscious Reagan imitator behaves this way, something serious is changing. The anti-government era of Ronald Reagan and Newt Gingrich has ended. A new era of big government is beginning.

What explains this? To put the answers simply: Politicians like big government; voters like big government; and the assumptions of small-government crusaders have recently been challenged.

Politicians like government

Consider politicians’ appetite for bigger government — an appetite that has always existed, even in the Republican Party of the 1980s and 1990s. As John Micklethwait and Adrian Wooldridge argue in their smart new book, “The Right Nation,” for every Cato Institute libertarian, the GOP harbors a moralist who wants government to regulate your private life; for every anti-tax crusader, there is a neocon who believes government should strive to instill such virtues as patriotism, educational discipline and marital fidelity. And that’s before you start counting the foreign policy hawks, who want more military spending, or the endless crony capitalists, who want government to hand out favors to their business buddies.

Those checks on the small-government wing of the Republican Party explain why, even in the Reagan years, federal spending rose by a quarter in real terms. But since then a change has come over the Republican Party. Because it has gained control of Congress, its cronyism has blossomed; far from disdaining the lobbyists who seek to expand pork-barrel spending, the congressional Republican leadership has created its odious “K Street Project” to ensure that lobbyists hire plenty of Republicans.

The Republicans, in turn, hire plenty of lobbyists. The head of the Republican National Committee is Ed Gillespie, who’s made a fortune peddling influence. His predecessor is Marc Racicot, who proposed initially to work as a lobbyist even while holding the top party job.

Next, consider voters’ appetite for big government. If you ask people what they want more of, the answer is quite likely to be things that the government provides: security (from local criminals and from terrorists), clean air and water, food whose safety is guaranteed by regulators, a health system for retirees, public education. As people grow more prosperous, such public goods probably matter to them more than private ones such as extra DVDs or fancier vacations. Hence the fact that as countries grow richer, the share of government spending in the economy nearly always goes up.

Voters appetite grows

Again, voters’ appetite for public goods always existed as a check on small-government crusaders; but, it has grown more powerful lately. There was a period when voters half-believed Reagan’s anti-government rhetoric and thought they’d be better off with fewer government programs. This made it possible for the Gingrich Republicans to push through various cuts in government, most notably the free-market farm law of 1996. But tolerance for Gingrichism proved exceedingly fleeting, and soon those rugged individualists of the heartland demanded a return to farm handouts. George W. Bush immediately obliged, and neither he nor his Democratic opponent have the courage to speak to voters honestly about entitlement reform.

Reagan period is over

All these forces for expanded government — the moralists and neocons, the crony capitalists, and the voters who want subsidies or public goods — could be held in check only by a countervailing intellectual consensus in favor of small government. Again, this existed in the Reagan period, when the economics profession spent most of its energy emphasizing the benefits of lower taxes and lighter regulation. But this, too, has changed lately.

The boom of the 1990s took place despite the 1990 and 1993 tax hikes; light regulation is now blamed for a raft of corporate fraud, California energy-trading scandals and Wall Street rip-offs. Big government is no longer seen as the principal enemy of a robust economy. Bad government — often meaning weak regulatory agencies that need more staff and funding — is now seen as an equal threat.

So if last week’s Reagan retrospectives emphasized his lasting influence on history, it’s worth remembering that his small-government crusade is one area in which his influence has come and gone. The dominant assumption of most political commentary in the 1990s — that, as Bill Clinton put it, the era of big government is over — now must be discarded. Political and intellectual forces, coupled with the swelling ranks of retirees, suggest an era of steadily bigger government is upon us.