After what even allies called a lost week, Donald Trump enters the last month of the presidential campaign dealing with yet another bad story — this one having to do with tax avoidance.

In the week since the first presidential debate, Trump has lost ground in key battleground state polls and is now facing an uproar over evidence that he may have used business losses of nearly $1 billion to avoid paying federal income taxes for nearly two decades.

October began with an unpleasant surprise for Trump: The tax story broke on Saturday night, capping a nightmarish week for the GOP standard-bearer that included a poorly reviewed debate performance, an argument with a former Miss Universe, and bad poll numbers.

Trump and his allies scrambled Sunday to contain the fallout from the New York Times story, arguing that the Republican presidential nominee’s tax history proves Trump is best qualified to fix the tax system.

“Oh, for gosh sakes,” New Jersey Gov. Chris Christie said on Fox News Sunday. “No apologies for complying with the law.”

Trump himself, in a tweet Sunday morning, said: “I know our complex tax laws better than anyone who has ever run for president and am the only one who can fix them.”

Former New York City mayor Rudy Giuliani said on ABC’s This Week, “He’s a genius at how to take advantage of legal remedies that can help your company survive and grow.”

The Hillary Clinton presidential campaign and other Democrats pounced on the story, saying that Trump has refused to release his tax returns because they would show he hasn’t paid any federal taxes in some years.

“This bombshell report reveals the colossal nature of Donald Trump’s past business failures and just how long he may have avoided paying any federal income taxes whatsoever,” said a statement from the Clinton campaign.

The campaign almost instantly created a website allowing users to calculate their taxes if they were paying as Trump did; the answer always comes up $0.00.

Former Democratic presidential candidate Bernie Sanders said the Trump tax story underscores the unfairness of the economic system. While the “rich are getting richer” and most other people are “getting poorer,” Sanders told This Week, “billionaires like Donald Trump are able to manipulate the tax system so that they avoid paying federal income tax.”

Trump and aides did not provide specifics about his taxes, and they did not indicate that he plans to release full tax returns.

Trump’s refusal to release his tax returns has been a constant source of criticism from Clinton and her allies.

The New York businessman says he doesn’t want to release his returns because they are under audit.

The Trump campaign also is ratcheting up its attacks on the news media. The campaign said the Times “illegally obtained” a 20-year-old document and applied a misleading spin.

While Trump has not denied the story, the campaign said in a statement that Trump “has paid hundreds of millions of dollars in property taxes, sales and excise taxes, real estate taxes, city taxes, state taxes, employee taxes and federal taxes, along with very substantial charitable contributions.”

Contributing: Paul Singer