He didn’t vote for Pauline Hanson’s racist motion. He wasn’t even in the Senate chamber when it happened.

Yet it was left to the government’s leader in the Senate, Mathias Cormann, to make a grovelling apology to the nation after Coalition MPs ‘mistakenly’ supported the One Nation leader’s motion claiming that “it’s OK to be white”.

“For me personally, this is severely embarrassing,” Senator Cormann said after Labor agreed to having another vote, which unanimously opposed the motion.

One Nation MPs were somewhere else, complaining to assembled journalists that “the most demonised person in this country is the white male”.

While that statement is highly debatable, Senator Cormann’s contrite appearance reminded us of a less contested view – that he is possibly the most diminished person in Australian politics right now.

Through recent misjudgements and political missteps, the once-formidable politician previously known as ‘The Cormannator’ has shrunk before our eyes.

Halcyon days

Not that long ago, Senator Cormann, 48, was feted by the media and other MPs for being a shrewd negotiator whose perseverance had secured the votes necessary to pass the bulk of the government’s company tax cuts as well as other key pieces of legislation into law.

He was recognised as one of the most influential politicians in the Turnbull government, teaming with fellow conservative and close personal friend Peter Dutton to not only advise Malcolm Turnbull but also hold off any leadership threats from the arch conservatives who coalesced around former PM Tony Abbott.

In fact, the role of Mathias Cormann in the Turnbull government was so pivotal that it was thought any leadership tilt would be doomed without his imprimatur, let alone active support.

Yet when the critical moment came, Senator Cormann’s renowned political skills failed him.

A most costly blunder

Instead of maintaining his integrity by sticking with Malcolm Turnbull until the government reached its inevitable conclusion at the federal election, Senator Cormann let himself fall for the fantasy being peddled by the Abbott camp to Peter Dutton – namely that they had the numbers to install Mr Dutton as Liberal leader.

In truth, they did not have the numbers. And if Mathias Cormann had not switched sides along with Mitch Fifield and Michaelia Cash, the motion to spill the leadership positions would have failed.

That’s not to say Malcolm Turnbull would be PM today if Senator Cormann had not given in to the impatience and ambition of others. The then PM was already mortally wounded after bringing on a surprise leadership ballot that saw Peter Dutton secure 35 votes to Mr Turnbull’s 48.

But at least if Senator Cormann had stuck with Mr Turnbull until the bitter end, he would have emerged with his integrity and reputation intact.

The fall guy

Since the failed leadership coup that elevated Scott Morrison instead of Peter Dutton, we’ve seen and heard very little from the government’s most senior minister in the Senate.

That was until the Prime Minister made it clear that Senator Cormann would be answerable to the media for the government Senate team’s ‘mistaken’ support for One Nation’s deliberately provocative motion.

Being made the fall guy for the imbroglio suggests the Senate leader’s authority has shrunk not only in our eyes but also in those of the PM.

It’s not yet known if that loss of authority extends throughout the parliamentary wing Liberal Party.

It is also unclear whether Senator Cormann still commands the significant bloc of conservative votes that made him an influential force within the party.

With the offensive One Nation motion resubmitted to the Senate and soundly defeated, the government will now try to pretend that the mass misjudgement by its senators didn’t even happen.

Perhaps in the broader scheme of things the event will be relegated to a political footnote.

It won’t be so easy for the incredible shrinking politician, Mathias Cormann, to rewrite his own political history.