The House Republican Budget trims mandatory spending by $203 billion over the next decade, a period when the federal government will spend more than $40 trillion.

How do Republicans justify such trifling cuts when they control the House, the Senate, and the White House?

"We'd like to have more than $203 billion," House Budget Committee Chairwoman Diane Black told us in an editorial board interview with the Washington Examiner. But? "We cannot touch Medicare."

And why not? "The President has already made that very clear, that Medicare was off the table."

Black added, "The President just did not want, because of his campaign promises, for us to delve into that this year."

This is what we hear from Republican after Republican these days, and it reflects a disheartening abdication of responsibility.

"The Congress shall have power…" Article I, Section 8 of the U.S. Constitution reads, "to pay the debts and provide for the common defense and general welfare of the United States."

Congress controls spending, and has historically treated the president's budgetary views as optional suggestions, even when he is specifying the needs of the various executive agencies he runs. Spending on entitlements and other transfers is even less connected to the president's proper domain.

Congress isn't supposed to defer to the President on reforms to mandatory spending. Congress has primary responsibility for ensuring that Medicare does not grow so large that it consumes an unsustainable portion of the economy.

"Almost all of the long-term deficit and debt that we face relates to the exploding cost of Medicare and Medicaid," President Obama said seven years ago, "almost all of it." He was right then, and the situation is even more dire today. Medicare ate up 15 cents of every dollar Uncle Sam spent in 2016, according to the Kaiser Family Foundation, and that will be 17.5 cents a decade from now. Medicare taxes, which are supposed to pay for Medicare Hospital Insurance, are not enough to cover expenses, meaning that the marginal Medicare Part A dollar comes out of general revenue. If you take solace in this shortfall being covered by the Medicare "trust fund," note that this accounting creature will be depleted by 2029.

Medicare spending is currently about 3.2 percent of GDP, and that's set to climb to 4.1 percent by 2027.

Republicans in Congress have many ideas for reforming Medicare. Paul Ryan, the Speaker of the House, has proposed slowly raising the retirement age and reducing the taxpayer subsidy to wealthier seniors. There are many other ideas popping around, and there's plenty of need. Republicans brag about cutting appropriations for tiny programs here and there, but if you don't fix Medicare's runaway growth, it won't matter. Much higher taxes, or much larger deficits, are in the future.

President Trump did say he wouldn't touch Medicare, but that doesn't bind congressional Republicans. They took over the House in 2010 on the strength of a Tea Party wave, driven by citizens furious about runaway deficits.

Trump said lots of things. He said he would repeal Obamacare, but the Senate hasn't done it, and House Republicans only nominally did it. Trump said he would build a wall, but the funding for that hasn't materialized. Trump opposed a Russian sanctions bill, but both chambers passed one by such a wide margin that he faced the choice of either signing it or having his veto overridden.

Even President Trump has disregarded the statements of candidate Trump on some things, such as his surge in Afghanistan. There's no reason for congressional Republicans to feel bound by Trump's Medicare promises.

If the President doesn't like a Medicare reform, he can propose a tweak, or make a compromise. You know, a deal. But Congress is giving him his main ask, up front, in exchange for nothing.

Congressional Republicans may be running from Medicare reform out of party loyalty, but they owe a higher loyalty to their country. And their country can't withstand runaway Great Society programs eating up larger and larger shares of the economy.