For months, Juliette Kayyem has treaded carefully around the word “collusion,” but Donald Trump Jr. is pushing her closer to the edge.

“I’ve always talked about it being a scale between all this information being benign to direct collusion, and as the months have gone on, each piece is leading towards collusion,” she said on Boston Public Radio today. “We just took two big steps towards collusion in terms of Donald Trump Jr.”

Trump Jr. tweeted out email correspondence today during which he agreed to meet with a Russian lawyer over information that might have hurt Hillary Clinton’s campaign in June 2016.

The emails were met with widespread condemnation and questions about the legality of a campaign official working with a foreign government to influence an election.

Kayyem said Trump Jr. is walking a thin line, since the content of the meeting is relevant and remains unconfirmed.

“It’s one thing to say you’ll take a meeting with a drug dealer, but unless you take the drugs, it’s hard to make a case,” she said. “The fact that he took the meeting ... to the Russian intelligence agencies and to Putin himself, their question is, do the Trump people know what to do with this? Will they tell on us? Are they receptive to our help?”

For Kayyem, the emails provide evidence that the Trump campaign was willing to keep secrets and receive assistance from the Russians, which is what’s bringing her closer to actually saying the c-word.

“I think we are so much closer to collusion at this stage than we were even on Saturday when the first news broke,” she said.

Kayyem also pointed out that Trump Jr. responded to the prospect of incriminating Hillary Clinton by saying “If it’s what you say I love it especially later in the summer,” a statement that has been a widely-cited part of the email release.

“They are also directing when you release the information,” she said. “They had a sophisticated strategy about when they wanted the information to leak.”

She suggested it’s unlikely that the administration will tighten ranks in the aftermath of this news.

“This is the stage of a criminal conspiracy investigation when it’s every man for himself,” she said. “At this stage, I’m not going to be surprised by anything.”

Juliette Kayyem is a national security expert, host of the SCIF podcast and a CNN and WGBH contributor. To hear her interview in its entirety, click on the audio player above.