Donald Trump is facing growing legal peril as the House January 6 committee lays out a case that appears increasingly geared to making a criminal prosecution all but inevitable.

The panel’s seventh hearing on Tuesday argued that Trump instigated an attack on the US Capitol that was premeditated rather than spontaneous and that he cannot hide behind a defence of being “willfully blind”.

The committee also sought to show an explosive convergence between Trump’s interests and those of far-right extremist groups, although critics said the case fell short of direct collusion.

Even so, the late revelation that Trump had tried to contact a person talking to the committee about potential testimony – raising the prospect of witness tampering – was only likely to compound pressure on the Department of Justice to investigate the former president.

Trump and his supporters have long claimed that the riot at the Capitol on 6 January 2021 was a peaceful protest against his election defeat that spun out of control in the heat of the moment. Nine deaths are linked to the attack and its aftermath.

But Tuesday’s hearing revealed evidence that the president planned in advance to send supporters, who he knew were armed, marching on the Capitol.

The panel showed a draft tweet, obtained from the National Archives, calling on supporters to arrive early for a rally and to expect crowds.

“March to the Capitol after. Stop the Steal!” the draft tweet said.

There were also fresh details about planning for Trump’s rally on the Ellipse outside the White House as aides scrambled to set up a second stage outside the Capitol complex, across the street from the supreme court.

In a 4 January text message from rally organiser Kylie Kremer to Trump ally Mike Lindell, the MyPillow chief executive, Kremer explained: “This stays only between us, we are having a second stage at the supreme court again after the Ellipse. [Trump] is going to have us march there/the Capitol.”

Kremer warned that if the information got out, others would try to sabotage the plans and she would “be in trouble” with the National Park Service and other agencies. “But Potus [Trump] is going to just call for it ‘unexpectedly,”’ Kremer wrote.

Stephanie Murphy, a Democratic member of the House committee, said: “This was not a spontaneous call to action, but rather was a deliberate strategy.”

The hearings have inflicted greater political damage on Trump than many expected. In opening remarks on Tuesday, Liz Cheney, vice-chair of the committee, noted how Trump loyalists have changed their approach to argue that he was manipulated by outsiders and “incapable of telling right from wrong”.

Believed to be one of the strongest advocates for a criminal prosecution, Cheney appeared to pre-empt a possible defence when she insisted: “President Trump is a 76-year-old man, he is not an impressionable child. Just like everyone else in our country, he is responsible for his own actions, and his own choices … and Donald Trump cannot escape responsibility by being willfully blind.”

Democrats and other critics said a potential DoJ case against Trump was stronger than ever and again adopted legal terms such as “premeditated”.

Hillary Clinton, the former secretary of state defeated by Trump in 2016, tweeted: “Trump was crystal clear about his wishes in the lead-up to January 6. What happened that day was not an accident or a coincidence. It was organized, deliberate, and premeditated.”

Norm Eisen, a former special counsel to the House judiciary committee, including for the impeachment and trial of Trump, wrote: “Yesterday’s hearing further established Trump’s violent intent. They’re moving from evidence of likely crime to proof beyond a reasonable doubt.”

Tuesday’s session focused in part on December 2020, a period when many Republicans were moving on from the November election Trump lost to Joe Biden.

There was testimony about an “unhinged” six-hour Oval Office meeting on 18 December that ran beyond midnight, in which, amid shouting and screaming, Trump resisted objections from White House lawyers to a plan to seize voting machines. The plan was eventually discarded.

As night turned to morning, Trump tweeted a call for supporters to come to Washington on January 6, when Congress would tally electoral college results.

“Be there. Will be wild,” Trump wrote.

This “call to arms” ricocheted around online echo chambers of Trump’s fanbase. The panel showed graphic and violent text messages and played videos of rightwing figures vowing that January 6 would be the day they would fight for the president. It would be a “red wedding”, said one, a reference to a mass killing in the TV series Game of Thrones. “Bring handcuffs.”

Some former Trump officials denied that the committee had tied him directly to extremist groups such as the Proud Boys and Oath Keepers. But calls for Merrick Garland, the attorney general, to prosecute Trump for the crime of encouraging the commission of crimes of violence are gathering momentum.

Laurence Tribe, a constitutional law professor at Harvard University, said of the latest hearing: “It greatly strengthens the case, particularly with respect to Trump’s direct involvement in fomenting the violence of the insurrection itself.

“The evidence that emerged was very powerful, indicating that [the riot] was anything but spontaneous, that he was fully aware at the time the unhinged meeting at the White House ended at around midnight on 18 December that his only remaining alternative was essentially to pull the trigger and issue the tweet at 1.42 in the morning, which included the dramatic call to action.”

This was predictably interpreted by the Proud Boys and the Oath Keepers and other violent white nationalist militia and Christian militia groups as the call to arms, Tribe said.

“So the former president’s direct responsibility for the riot, for the insurrection, is now much easier to prove and it would be increasingly problematic for the attorney general not to authorise a full-blown investigation into the president’s direct responsibility for the federal offence that involves.”