President Barack Obama says it’s time to “get it done.” Unfortunately, his remarks last week did little to encourage a deal raising the debt ceiling and cutting the deficit.

Rather, he further poisoned the atmosphere. If anyone thought that in his news conference Obama would offer a fresh approach, they were mistaken. Among other things, he said it was time to whack the oil companies and the rich — the oldest chestnuts in the Democrats’ rhetorical grab bag. He falsely framed the issue as a choice between tax breaks for corporate jet owners and scholarships for kids.

For their part, the Republicans remain dead set against any tax increase.

While both sides are still playing to their base, more behind-the-scenes progress has occurred than the participants’ public statements suggest. Gerald Seib of the Wall Street Journal reports that negotiators have agreed, at least in principle, on perhaps $2 trillion in spending cuts.

More broadly, there are other signs that the political climate is changing. AARP, the very embodiment of the senior-citizen entitlement mentality, admitted that Social Security benefits might have to be trimmed, although the organization later claimed it was misunderstood. A majority of senators voted recently to end ethanol subsidies, an amazing departure from past positions.

So perhaps a substantive deal is doable, despite the venomous atmosphere. Democrats will have to climb down from their soak-the-rich sanctimony, and Republicans will have to drop their opposition to measures that will bring in more revenue.

The GOP is right to oppose higher tax rates. But cleaning loopholes and exclusions out of the tax code — in exchange for substantially lower rates — is the way to proceed, as the Simpson-Bowles deficit commission concluded late last year.

Loopholes and credits are known as “tax expenditures.” In terms of the effect on the Treasury, they have the same effect as handing out cash.

Tax credits for solar panel purchases and hybrid cars, deductions for mortgage interest — these special deals and loopholes add up to about $1 trillion a year. As we learned from the tax reform effort of 1986, the way to clean out loopholes is to combine such reforms with lower tax rates.

But that leaves us with the knotty problem of which loopholes to eliminate. They all have fierce defenders. Many are extremely popular, such as the deduction for mortgage interest.

Harvard’s Martin Feldstein and other economists at the National Bureau of Economic Research have been working on a reform that could solve this problem.

Their idea? Limit how much a taxpayer can claim in total credits and deductions. Feldstein suggests a cap of 2 percent of total income, which he says would produce $278 billion a year in additional revenue. A 5 percent cap, with more room for deductions, would bring in $110 billion.

Obviously, the rate at which the caps would be set would be negotiable, along with the deductions and exclusions covered by the cap. Feldstein’s plan would not include tax breaks linked to savings and investment, such as the deduction for individual retirement account contributions, interest accrued in IRAs or the lower tax rate for capital gains. Many would argue that the charitable deduction should also be excluded from the cap.

Under this plan, Feldstein writes, “individuals would continue to benefit from all of their current deductions, exclusions and credits. It is the total tax benefit and not any particular tax reduction that is limited.”

Recently, former Federal Reserve governor Lawrence B. Lindsey wrote that our fiscal situation is more ominous than many believe. He gave three reasons, but I’ll just cite one: Interest rates are unusually low. If and when they return to normal, the Treasury’s financing costs will explode. By 2020, Washington could be paying more than $700 billion a year more than currently projected merely to service the national debt.

It’s probably not possible to climb out of this hole without more revenue. The plan Feldstein proposed would pull in more without raising marginal tax rates — which are key to the incentives to work, invest and undertake entrepreneurial risk. A good plan would broaden the base, lower the rate and, yes, bring in more revenue.

E. Thomas McClanahan is a member of the Kansas City Star editorial board.