Politically, by discussing such a sensitive topic that could prove embarrassing if revealed, Trump Jr. and the other Trump campaign officials in the room for the meeting with Russian attorney Natalia Veselnitskaya, including Jared Kushner and Paul Manafort, may have also exposed themselves to future blackmail threats, the legal experts said.

Those potential troubles deepened Monday night with a fresh New York Times report alleging that Trump Jr. was sent an email before his meeting with Veselnitskaya indicating the information she had was part of a Russian plan to boost his father in the race against Clinton.

Trump Jr. first described the Veselnitskaya meeting in a Saturday statement to The New York Times, framing it as a discussion about a program for adoption of Russian children that the Kremlin canceled to retaliate for a U.S. law targeting Russian human rights abusers. But Trump Jr. expanded on his explanation on Sunday, saying the Trump Tower meeting was initially presented to him as a chance to obtain opposition materials about Clinton.

In his Sunday statement, Trump Jr. said Veselnitskaya gave only “vague, ambiguous” statements during their 20- to 30-minute meeting and that she didn’t have any “meaningful information” about Clinton. Trump Jr. also said he didn’t know the name of the Russian lawyer before their meeting.

Trump Jr. has hired New York criminal defense attorney Alan Futerfas as his personal attorney for Russia-related matters, Futerfas told POLITICO. On Monday, the president’s son sought to quell the political firestorm by criticizing media coverage about it and insisting that what he did was not unusual for someone in the midst of a presidential campaign. He also emphasized that the meeting “went nowhere.”

On Monday night, Futerfas responded to the most recent report saying it was “much ado about nothing” and adding that “the bottom line” is that Trump Jr. did “nothing wrong.”

But legal experts of both political parties say his explanations may not fly if he’s questioned under oath by Congress or Robert Mueller, the special counsel investigating potential Trump campaign collusion with Russia — and where perjury and making false statements carry legal consequences that don’t exist when engaging with reporters or on social media.

“I don’t think that is an out,” said Robert Bauer, a former White House counsel under President Barack Obama and the Democrat’s 2008 campaign attorney. “If they accept the meeting on the understanding that they will be offered something of value — the opposition research — they are sending a clear signal that they would like to have it.”

Bauer added that accepting a meeting where there’s an understanding of purpose “raises a question under the federal campaign finance law” for which Trump Jr. could be held accountable.

Maine GOP Sen. Susan Collins, a member of the Senate Intelligence Committee, and California Rep. Adam Schiff, the top Democrat on the House Intelligence Committee, have both said their panels should interview Trump Jr. On Monday afternoon, Trump Jr. said he plans to cooperate with the investigations. “Happy to work with the committee to pass on what I know,” he tweeted.

A spokesman for Mueller declined comment about whether he would investigate the meeting.

Legally, Trump Jr. now finds himself in the same boat as a number of other Trump campaign aides already facing scrutiny for their connections to Russia, from former campaign chairman Paul Manafort’s work on behalf of pro-Kremlin officials in Ukraine to former White House national security adviser Michael Flynn, who is under scrutiny on multiple fronts, including for lobbying on behalf of a Turkish businessman with ties to Russia. The president himself is also reportedly the subject of an obstruction of justice probe by Mueller for firing FBI Director James Comey.

It’s far from clear whether Trump Jr. will end up facing any charges related to his meeting, but several lawyers said there is plenty of fodder for investigators to look at.

“This is treason,” Richard Painter, a former George W. Bush White House ethics lawyer, wrote Sunday night on Twitter. “He must have known that the only way Russia would get such information was by spying.”

Painter added in another message: “In the Bush administration we could have had him in custody for questioning by now.”

Jennifer Taub, a white-collar attorney and Vermont Law School professor, posted on Twitter a 20-part message Monday that cited a specific section of the U.S. criminal code that Trump Jr. may have crossed concerning prohibitions on conspiracy to defraud the U.S. “Potential indictments are coming into clear focus,” she wrote.

Former Bill Clinton White House counsel Jack Quinn said Trump Jr.’s meeting to discuss opposition research during a campaign “is not in and of itself illegal.” But Quinn nonetheless said it “will be a subject of exploration by Mr. Mueller.”

Norm Eisen, a former chief White House ethics attorney, called the Trump Jr. meeting with the Russian lawyer “very unusual” and cited several parts of federal criminal statute that may have been breached, including the Logan Act, a 1799 law barring private citizens from interfering with diplomatic relations between the U.S. and foreign governments. The law has been enforced only once — more than 200 years ago — but still remains a potent political cudgel.

“In decades of working on campaigns and as an election lawyer, I have never personally witnessed or authorized anything like this,” Eisen said. “In a normal campaign, this would be the most crimson of red flags and would not be undertaken without counsel and candidate consent, which raises the question of whether Trump himself had any indication of this.”

Eisen also said the Trump Jr.- Veselnitskaya meeting raises questions about whether “the Trump campaign welcomed Russian help in the form of dirty tricks; if so, that could confer conspiracy liability for any Russian cyber or other crimes that followed.”

GOP and Democratic campaign operatives said Trump Jr. wasn’t practicing the typical behavior one does when dealing with potential opposition research.

“Running @marcorubio camp lots of random people asked to meet to share “secret oppo” I was just never dumb enough to meet w/ them #ButWeLost,” Terry Sullivan, the former campaign manager for Sen. Marco Rubio’s 2016 GOP primary campaign, posted Monday on Twitter.

Republican strategist Stuart Stevens also posted Sunday night on Twitter about the unusual nature of the Trump Jr. meeting. “When Gore campaign was sent Bush debate brief book, they called FBI. If foreign interests offer you info on former SOS, you call the FBI,” he wrote.

In an email, former Clinton 2016 campaign manager Robby Mook questioned why the Trump campaign officials would take a meeting “with an associate of a hostile nation state regarding the campaign without knowing the name or identity of that person, just they were Russian and that person had damaging information about Hillary.”

“The danger of that speaks for itself,” he added. “It gets us one step further to collusion, but also raises serious questions about whether Kushner and others in the Trump administration should be conducting our foreign policy. Staff who have lied about, or concealed meetings with Russians or who have hidden financial ties to Russian oligarchs should be barred from seeing classified information or participating in policymaking until Congress can determine whether they will act in the public interest.”

Jennifer Psaki, the former Obama White House communications director and State Department spokeswoman, also used a previous presidential campaign as an example for pointing out the unusual nature of the meeting. “Imagine if @davidplouffe met with Chinese lawyers with dirt on @SenJohnMcCain. NOT standard for either party to get oppo from foreign agents,” she wrote on Twitter.

Trump Jr. responded to the latest chapter in the evolving Russia scandal with a series of Twitter posts Monday morning criticizing the news media for their coverage of the story. He shared a New York Post article that called the original New York Times coverage a “big yawn.” He argued that his explanations to the media had not changed. “No inconsistency in statements, meeting ended up being primarily about adoptions. In response to further Q’s I simply provided more details,” he wrote.

And Trump Jr. — whose representatives did not respond to a request for comment for this story — insisted he hadn’t done anything different concerning opposition research compared to other political candidates.

“Obviously I’m the first person on a campaign to ever take a meeting to hear info about an opponent…went nowhere but had to listen,” Trump Jr. wrote.

Gabriel Debenedetti contributed to this report.