New York (AFP)

They have been thought invalid for months, but Donald Trump and the Republicans are constantly putting conspiracy theories on the table as part of the congressional hearings, giving them unprecedented visibility.

A server containing emails from Hillary Clinton who reportedly disappeared in Ukraine, or Ukrainians - rather than Russians - who allegedly tried to influence the US presidential election 2016: many of these theses come back regularly in the context of these hearings .

On Thursday, it was Fiona Hill, former head of the National Security Council, who insisted that the thesis of Ukrainian interference in the US presidential election was "a fiction".

On Tuesday, Kurt Volker, former US envoy to Ukraine, dismissed as "not credible" the idea that Joe Biden or his son, Hunter, would be involved in a corruption scandal in Ukraine.

However, the Republican Devin Nunes, No. 2 of the parliamentary committee that conducts hearings, does not cease to evoke these theses, as well as prominent conservative personalities, like the son of President Donald Trump Junior or the presenter Fox News star Sean Hannity. Theories often relayed on Twitter by the president himself.

The hearings confirm, if necessary, the wide audience that now benefits the conspiracy ideas.

While the internet has been fertile ground for their development for 20 years, they remained until recently confined to margins. With the election of Donald Trump, they now have access to the highest levels of power, say several analysts.

Professor of Political Science at the University of Miami, Joseph Uscinski recalls that before Donald Trump, other American presidents have espoused conspiracy theories, including Republican Richard Nixon, also targeted by impeachment proceedings.

"But he did not talk about it very openly," he says. "Trump is the opposite (...) He uses it to motivate people who are a little on the margins of the Republican Party (...) and to ward off criticism. was elected".

Conspiracy theories are not new, from September 11 to the birthplace of Barack Obama, through the first mission on the moon inhabited.

But according to Eric Oliver, professor of political science at the University of Chicago, such assertions have spread much more widely among US conservatives with the rise of the Christian right since the 70s.

In this movement, many voters for whom intuition takes precedence over knowledge. "They also often believe in the supernatural and the Apocalypse, which fits well with a conspiracy view" of things.

It's hard to know how much this population represents today in the American right. For Joseph Uscinski, nothing shows that conspiracy theories are more popular today than in recent decades.

A few days ago, Eric Oliver conducted a poll that revealed, among other things, that 18% of respondents believed the rumor of Ukraine's involvement in the 2016 US election.

- Democracy in danger? -

Very fashionable in recent years, fact-checking journalism has little impact on these Americans, according to several observers. "Often," says Eric Oliver, "when people are subjected to facts that disturb their beliefs, they sweep them away and move on."

Joseph Uscinski also sees traces of this movement in the Democratic camp, mainly among supporters of Bernie Sanders, for whom "the richest 1% control politics and the economy, which is not true".

For Jonathan Kay, author of the book "Among the Truthers", "it does not matter if one is right or left".

"Anyone who is envious of power or feels his power weakened is exposed to conspiracy theories," he says, citing as an example the conspiracy literature around 9/11, which originated on the left. The conspiracy theses "offer people a bridge between what they see and what they believe," he says.

If these analysts believe that the new visibility of these conspiracy theories is unlikely to pass anyone from one camp to another, they worry about its consequences on the American political debate.

"Modern democracies rely on a form of rationality in the discourse," says Eric Oliver. "They are in danger when this speech is undermined by demagogues and conspiracy theories".

For Joseph Uscinski, there is a risk that the president may base some of his decisions on these false theories, or incite others to draw inspiration from them.

Until now, Eric Oliver saw this line conspiracy primarily as a political instrument for Donald Trump. But his insistence on seeing Ukraine announce an investigation into the Biden "makes me think he really believes it."

© 2019 AFP