Whatever happened to the deficit hawks?

When Barack Obama was president, congressional Republicans were deficit hawks. They opposed almost everything Obama wanted to do by arguing that it would increase the federal budget deficit.

But now that Republicans are planning giant tax cuts for corporations and the wealthy, they’ve stopped worrying about fiscal responsibility.

Senate Republicans have agreed on a budget that would cut taxes by $1.5 trillion over the next decade, which could mean the biggest budget deficits in history.

Unless Republicans want to cut Social Security, Medicare and defense, that is. Even if Republicans eliminated everything else in the federal budget, they wouldn’t have nearly enough to pay for tax cuts of the magnitude they are now touting.

But Republicans won’t cut Social Security or Medicare because the programs are overwhelmingly popular. And rather than cut defense, Senate Republicans want to increase defense spending by $80 billion (enough to fund the free public higher education that Bernie Sanders proposed in last year’s Democratic primary — which deficit hawks in both parties mocked as being ridiculously expensive).

There’s also the cleanup from Hurricanes Harvey and Irma, estimated to be at least $190 billion. And President Donald Trump’s “wall,” which the Department of Homeland Security estimates will cost $22 billion. Oh, and don’t forget infrastructure. So how do Republicans propose to pay for any of this — and provide a big tax cut for corporations and the wealthy — without exploding the federal deficit?

Easy. Just pretend the tax cuts will cause the economy to grow so fast — 3 percent a year on average — that they’ll pay for themselves, and the benefits will trickle down to everyone else.

If you believe this, I have several past GOP budgets to sell you, extending back to Ronald Reagan’s magic asterisks.

The Congressional Budget Office and the Joint Committee on Taxation don’t believe it. They realistically assume that the economy won’t grow over 2 percent a year on average over the next decade. The Federal Reserve estimates the fastest sustainable rate of economic growth will be 1.8 percent, given how slowly America’s workingage population is growing, as well as the slow rate of productivity gains.

But Trump has already made a fetish out of discrediting anyone who comes up with facts he doesn’t like.

Unfortunately for all the Republican tax cutters who used to be deficit hawks, we already have real-world historical evidence of what happens after massive tax cuts. Reagan and George W. Bush cut taxes on the wealthy and ended up with huge budget deficits.

Besides, there’s no reason to cut taxes on big corporations and the wealthy. If anything, their taxes should be raised.

Trump says we’re “the highest taxed nation in the world.” Rubbish. The most meaningful measure is taxes paid as a percentage of GDP. On this score, the United States has the fourth-lowest taxes of any major economy. (Only South Korea, Chile and Mexico rank lower.)

American corporations aren’t overtaxed. After taking deductions and tax credits, the typical U.S. corporation today pays an effective tax rate of 24 percent. That’s only a tad higher than the average of 21 percent among advanced nations.

The rich aren’t overtaxed. The wealthiest 1 percent in the U.S. pay the lowest taxes as a percentage of their income and total wealth of the top 1 percent in any major country — and far lower than they paid in the U.S. during the first three decades after World War II, when the American economy grew faster than it has been growing since the Reagan tax cuts.

But we do have a deficit in public investment — especially in education and infrastructure. And we do have a national debt that topped $20 trillion this year and is expected to grow by an additional $10 trillion over the next decade.

What’s the answer? Raise taxes on big corporations and the wealthy. That’s what rational politicians would do if they weren’t in the pockets of big corporations and the wealthy.