Justin Amash, who left Republican Party, poised for presidential run as Libertarian

Congressman Justin Amash of Michigan said late Tuesday that he is launching an exploratory committee for the 2020 Libertarian Party's presidential nomination.

The Republican-turned-independent said on Twitter that the U.S. is ready for new leadership. He also posted a link to a new campaign website.

"Americans are ready for practical approaches based in humility and trust of the people," Amash said. "We're ready for a presidency that will restore respect for our Constitution and bring people together."

Amash, 40, announced last July that he was leaving the Republican Party, saying he had become disenchanted with partisan politics and "frightened by what I see from it."

He announced his decision in an editorial published in the Washington Post, where he lamented "a mindset among the political class that loyalty to party is more important than serving the American people or protecting our governing institutions."

He drew criticism from President Donald Trump and fellow Republicans when he said the president had engaged in impeachable conduct as described in special counsel Robert Mueller's report on ties between Trump's 2016 campaign and Russia.

Amash then supported the congressional impeachment inquiry into Trump's foreign policy dealings with Ukraine. Trump became just the third U.S. president to be impeached Amash was the lone non-Democrat to vote in favour of both articles of impeachment but was then acquitted in the Senate in a vote that fell along partisan lines.

Trump has called Amash a "total loser."

Congressional campaign paused

Amash, representing a district in Grand Rapids, has won five congressional elections over Democratic opponents.

When asked by Reason.com in an interview Wednesday to clarify his status for the November 2020 vote in his district, Amash said: "My campaign is paused, but frankly, I'm running this campaign for president, and I don't intend to return to my congressional campaign."

He also took shots at both major candidates in the interview, saying Trump changes positions on issues "week to week, but Joe Biden has also held multiple positions over his lifetime."

While broadly speaking there's more overlap between Republican and Libertarian Party voters than with Democrats and Libertarians, Amash's effect in a general election would be uncertain.

Libertarian candidate Gary Johnson received 4.5 per cent of the 2016 presidential vote, the leader of among the candidates not named Trump or Hillary Clinton who amassed an overall total of 7.1 million votes.

Academics studying the large number of votes outside of the major two parties relative to recent elections have not come to a consensus on whether it helped Trump or narrowed his victory.

Decades before Johnson, David Koch ran as vice-president on the Libertarian Party ticket in 1980. Koch and his older brother, Charles, Kansas energy industry executives, then decided after a poor showing they would have a more lasting impact on public policy objectives outside of electoral politics.

Beginning in the 1990s, they began to wield considerable influence behind the scenes on Republican Party positions through hundreds of millions in funding to a number of think-tanks and free-market-oriented business programs in U.S. academic institutions.