The US Senate acquittal of Donald Trump was on expected lines. This was Trump’s second impeachment trial in a year, with fellow Republicans blocking conviction over the former president’s role in the deadly assault by his supporters on the US Capitol.

Impeachment trials are rare, Senators meeting as the court of impeachment over a president only four times in the nation’s history, for Andrew Johnson, Bill Clinton and now twice for Trump, the only one to be twice impeached. There have been no convictions.

Unlike last year’s impeachment trial of Trump in the Ukraine affair, a complicated charge of corruption and obstruction over his attempts to have the foreign ally dig up dirt on then-campaign rival Biden, this one brought an emotional punch displayed in graphic videos of the siege that laid bare the unexpected vulnerability of the democratic system.

At the same time, this year’s trial carried similar warnings from the prosecutors that Trump must be held accountable because he has shown repeatedly he has no bounds. Left unchecked, he will further test the norms of civic behaviour, even now that he is out of office still commanding loyal supporters, they said.

Anything that Trump does makes for great headlines, and the media knows that full well. If anything, the trial has continued to put the former President in the limelight, even after his term was over.

Trump’s behaviour leading up to and during the 6 January insurrection at the US Capitol continued dominating conversation in political circles in anticipation of his second impeachment trial, which commences on Tuesday.

An impeachment measure is similar to a criminal indictment, but Trump does not seem to be unnerved. Rather, he appears to be resilient, defying all odds. Trump is only the third president ever to be impeached by the House of Representatives and the first to be impeached twice and the first to face an impeachment trial after leaving office. But the Senate still has never convicted an impeached president.

 Democrats forged ahead with impeachment despite knowing it could overshadow critical early weeks of Biden’s presidency.

The House approved the single article of impeachment against Trump on Jan.13, with 10 Republicans joining the chamber’s Democratic majority. That vote came a week after the pro-Trump mob stormed the neoclassical domed Capitol, interrupted the formal congressional certification of Biden’s victory, clashed with an overwhelmed police force, invaded the hallowed House and Senate chambers, and sent lawmakers into hiding for their own safety.

Impeachment, once a rare occurrence, has become more commonplace during America’s era of poisonous political polarisation in recent decades. In the 209 years after the first US president, George Washington, took office in 1789, there was only one impeachment.

Since 1998, there have been three, including Trump’s two. Andrew Johnson was impeached and acquitted in 1868 in the aftermath of the American Civil War and Bill Clinton was impeached in 1998 and acquitted in 1999 of charges stemming from a sex scandal.

Richard Nixon resigned in 1974 rather than face impeachment over the Watergate scandal.

Trump’s acquittal does not end the possibility of other congressional action against him such as a censure motion. Republicans seemed dead set against an idea floated by Democrats of invoking the Constitution’s 14th Amendment provision barring from public office anyone who has “engaged in insurrection or rebellion” against the government.

The impeachment proceedings also can be viewed in the context of a battle for the future of the Republican Party.