Tough lesson for Trump: It's hard to do big things in D.C.

During the campaign, President Trump said the big stuff would be a snap. "You're going to be sick and tired of so much winning."

Obamacare repealed and replaced. Taxes cut. A trillion dollars of infrastructure spending coursing through the economy. A beautiful wall rising on the southern border. No problem!

Reality is setting in now. Even with fellow Republicans in control of both houses, Congress is balky: hyperpartisan, riven by intraparty disagreements and factions, and subject to interest-group pressure. On top of those dynamics, there is the fiscal straitjacket of federal budgeting.

"It's still hard to do big things in D.C.," said Dan White, director of fiscal policy research for Moody's Analytics, the economic forecasting firm.

In retrospect, the implosion of efforts to replace the Affordable Care Act seems inevitable. Throughout history, Congress has never repealed a major social-benefits program once it has taken effect. Social Security and Medicare and Medicaid have survived 82 years and 52 years, respectively. And though it has had problems, the ACA expanded Medicaid to give health coverage to millions of working-class Americans.

Most GOP governors who accepted the Medicaid expansion did not want to see health coverage for their residents rolled back. Concerns about the possibility animated the party's moderate lawmakers whose opposition to the repeal bill arguably doomed it.

"For generations, entitlements have been referred to as the 'third rail' of politics, and that about sums it up," said Charlie Gerow, a Republican strategist in Harrisburg who got his start working on Ronald Reagan's campaigns.

"Anybody who believes that a 2,700-page piece of legislation didn't have a lot of roots dug deep, that would require a lot of hacking to get rid of, doesn't understand how things work," Gerow said. "Once you have something that you believe you are entitled to, you cling to it."

In addition to the 11 million who got health insurance for the first time through the Medicaid expansion or federal subsidies to buy private policies, the law prohibited insurers from denying coverage for pre-existing conditions and mandated coverage of some services.

After Franklin Delano Roosevelt signed Social Security into law in 1935, Republicans ran on repealing it for almost two decades, portraying the program as an un-American redistribution of wealth. In 1952, though, Dwight Eisenhower embraced Social Security. He said that the GOP had to modernize to survive and even proposed limited medical coverage for the elderly, though conservative Barry Goldwater blasted Ike for a "dime-store New Deal."

In 1964, Democrat Lyndon Johnson swamped Goldwater and in the brief window after the landslide coaxed Medicare and Medicaid through Congress, along with civil rights legislation.

Republicans Richard Nixon and Gerald Ford left Medicare and Medicaid alone. But Gerow's hero, Reagan, campaigned against Medicare as "socialized medicine" when it was enacted in 1965, but eventually became reconciled to the program.

And early in his first term, Reagan backed down amid fierce opposition to a relatively modest attempt to trim Social Security by cutting early-retirement benefits. He agreed to a bipartisan commission, which in 1983 led to an agreement with Democrats to extend the long-term solvency of Social Security by raising the payroll tax and the retirement age, among other changes.

In 2005, President George W. Bush, newly reelected, pushed a proposal to allow younger people to invest some of their Social Security savings in private investment accounts. He got nowhere with the idea.

"I'm not going to cut Social Security like every other Republican, and I'm not going to cut Medicare or Medicaid," Trump promised during the campaign. Health and Human Services Secretary Tom Price, however, wants to switch Medicare to a "premium support" program -- the government would provide a fixed amount for seniors to purchase private insurance. Leading House Republicans also support that idea. As the entitlement programs continue to consume an  ever larger share of the federal budget, Trump's resolve could be tested.

The failure to repeal Obamacare could upend Trump's plans to cut taxes. He had planned to use savings from the repeal to offset revenue loss by reductions in corporate and income taxes.

White, the Moody's analyst, said the firm predicts that a reduction in the 35 percent corporate tax rate might happen; it would generate some revenue from U.S. corporations "repatriating" cash from their foreign operations. But the possibility of major personal-income tax cuts is much murkier, he said.

For structural budgetary reasons, it was always going to be hard to get tax cuts, infrastructure spending, and the border wall passed, on top of Trump's plan to increase defense spending.

"There are no easy choices left," White said. "We're past the point we can borrow our way out of things." The national debt is close to its highest levels since World War II, at about 104 percent of the yearly Gross Domestic Product, the value of goods and services produced in the United States.

In addition to debt, Social Security, Medicare and Medicaid costs are growing. White noted that the CBO projects that if nothing changes, 92 cents of every federal dollar will be spent on entitlements and interest on the debt by 2020.

"That leaves 8 cents for all discretionary spending, everything from aircraft carriers to Zion National Park," White said. "The longer we wait, the more difficult it gets."

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