Hillary Clinton and the Democratic Party spent $1 million a day more than Donald Trump and the GOP in the presidential race last month — only to see her lead in the polls shrink both nationally and in key swing states.

The Clinton campaign and the Democratic National Committee spent $78 million in August, according to Federal Election Commission disclosures.

In contrast, Trump and the Republican National Committee went through $47 million.

But despite being significantly outspent, Trump is in a tight race with his rival, polls show.

The RealClearPolitics average of national polls in a two-way race gives Clinton 45.4 percent to Trump’s 43.5 percent.

The Fox News Electoral Scorecard also shows close races in several battleground states.

New Hampshire and Colorado are now rated as toss-ups after being scored as leaning Democratic.

Minnesota is now rated as leaning Democratic, after having been solidly in Clinton’s column.

And Iowa was categorized as leaning Republican after having been rated a toss-up.

Analysts questioned if the power of TV ads, where most of Clinton’s money is going, might be fading.

“It makes you wonder about the real power of TV ads. And Trump won the nomination with little paid advertising,” University of Virginia political scientist Larry Sabato told The Post.

“Of course, you have to ask this: Would Clinton have fallen further without her advertising? Impossible to say.”

The GOP nominee has bragged on the stump about his relatively tight spending.

“Our expenditures on advertising, our expenditures on people, our expenditures on everything are a tiny fraction. And yet, we’re minimum tied,” Trump said Tuesday in Kenansville, NC.

“If you can spend less and be winning, that’s a positive thing, right?”

Clinton is running a conventional operation featuring multimillion-dollar ad buys and expansive voter outreach.

She spent about $10 million per week on TV and $1.3 million on polling in August. Her campaign has 800 employees.

Trump has kept spending down by enjoying seemingly limitless free media coverage and outsourcing the guts of his voter contact duties to the Republican Party.

His campaign has only about 130 employees and 100 consultants.

With Post Wire Services