The campaign of the long-shot Green Party candidate, Jill Stein, has spent $189,000 more on TV advertising for the general election than the Republican nominee, Donald Trump. Trump is also being out-spent by the campaign of the Libertarian candidate, according to a report from NBC News. Gary Johnson has outspent Trump by $15,000.

Why so close? Because Johnson has spent almost nothing — just $15,000 in total. And Trump has spent exactly nothing.

Some PACs supporting Trump have reserved ad time, spending a little over $8 million. That's less than 10 percent of what the campaign of Hillary Clinton and PACs supporting her have spent.

Clinton, for example, has a national TV buy that's running during the Olympics. The campaign has spent $13.6 million on NBC and its affiliates to advertise during Olympics coverage, according to the AP. This is similar to what President Obama and former Massachusetts governor Mitt Romney did in 2012. "I'd love to know what they're waiting for," one Romney veteran said of the Trump campaign.

Especially since waiting only makes the problem worse. The longer the Trump campaign waits to reserve ad time, the less ad time exists to buy and the more ads cost. During a presidential general-election year, candidates are competing with each other for ad space, but also with people running for the Senate, the House and local office. If you want to buy ads on local news in Pennsylvania, for example, you're competing with a lot of other campaigns for those 30 seconds. To the glee of station owners, that helps drive up prices.

In 2012, Romney's campaign and its allies spent $16 million in New Hampshire alone. They spent $5 million in Virginia in just the week before the Republican convention that year. Trump is at $0.

So what's Trump spending his money on? We won't have detailed numbers for his July spending until later this month, but we know where he spent his money through June.

The biggest chunk was actually on advertising, including on television, in early primary states. That's primary spending, not general — and even then, it wasn't that much. By January, the pro-Jeb Bush group Right to Rise had already spent $50 million in advertising. Through December, Trump's campaign had spent a little over $1 million on a broad variety of advertising costs.

His biggest spending category in June was on fundraising consultants, since that was the first month he actually started officially raising money.

(What's "management"? Things like general consulting costs — and, in June, more than $200,000 on legal consulting.)

Trump has cash in his campaign accounts to spend. He's bought ads in the past. Why he's not doing so now — why the Green Party candidate is spending more than the Republican Party candidate, with about 90 days left until the election — is a question that defies a logical answer.