White House spokesman called a news site a 'left-wing blog' - and the news site fired back

Investigative journalism site ProPublica fired back at Sean Spicer on Monday, after the White House press secretary called it a "left-wing blog" and downplayed its report on President Donald Trump's finances.

The report, published on Monday, claimed an unreported clause in Trump's trust document allows the president to draw money from his 400 businesses without disclosing it.

When confronted with the report at his daily press briefing, Spicer attempted to discredit the source.

"I'm not aware there was any change" to the trust, Spicer said. "Just because a left-wing blog makes the point of something changing doesn't mean it actually happened."

The response from ProPublica was fierce. In a lengthy series of tweets, the nonprofit news site picked apart Spicer's claim and defended itself from the accusation of partisan bias.

First, ProPublica set out to prove Trump's trust document had, in fact, been changed to allow Trump to draw money from his businesses without disclosing it.

Next, it sought to prove its journalistic merit by reviving previously published investigative pieces that were damaging to the Trump administration.

Then, it combated Spicer's "left-wing" accusation by providing examples of times it published reports embarrassing to President Barack Obama.

All that was left was to stick the landing.