Joe Biden has claimed that Donald Trump is “scared to death” that he’ll be the Democratic nominee, after a Republican senator suggested the ongoing impeachment trial could damage the former vice president’s standing in Iowa.

The comments, from Iowa senator Joni Ernst, were quickly seized upon by political observers, who suggested that the Republican was verbalizing what has so-far been an unsaid intent to damage Mr Biden’s chances.

“Caucuses are this next Monday evening,” Ms Ernst said on Monday after a session in the Senate where Mr Trump’s team mounted its defence. “And I’m really interested to see how this discussion today informs and influences the Iowa caucus voters, those Democratic caucus goers. Will they be supporting vice president Biden at this point?”

Mr Biden has seized on those comments, which followed after Mr Trump’s legal defence team argued that Mr Biden should be investigated for corruption or abuse of power for his efforts as vice president to ensure the dismissal of Ukraine’s former prosecutor general, which he did while his son Hunter was on the board of the Ukrainian energy company Burisma.

“Iowa caucus-goers take note,” Mr Biden tweeted. “Joni Ernst just spilled the beans. She and Donald Trump are scared to death I’ll be the nominee. On Feb 3rd, let’s make their day.”

All the president's lawyers: The team fighting Trump's impeachment Show all 6 1 /6 All the president's lawyers: The team fighting Trump's impeachment All the president's lawyers: The team fighting Trump's impeachment Alan Dershowitz Dershowitz is a controversial American lawyer best known for the high-profile clients he has successfully defended. Those clients have included OJ Simpson, Jeffrey Epstein and Harvey Weinstein. One longtime Harvard Law associated told the New Yorker Dershowitz "revels in taking positions that ultimately are not just controversial but pretty close to indefensible." Getty All the president's lawyers: The team fighting Trump's impeachment Ken Starr Starr became a household name in the 1990s as the independent counsel who led the investigation that led to Bill Clinton's impeachment. That investigation began as a look into a real estate scandal known as Whitewater, and eventually led to impeachment after Mr Clinton lied under oath about having an affair with White House intern Monica Lewinsky. AP All the president's lawyers: The team fighting Trump's impeachment Jay Sekulow Sekulow is the president's longtime personal attorney, and, now, personal lawyer in the White House. He has been accused by former Rudy Giuliani associate Lev Parnas of being "in the loop" during the Ukraine scandal. Getty All the president's lawyers: The team fighting Trump's impeachment Pam Bondi Bondi is the former attorney general in Florida, and a longtime backer of the president's. She made a name for herself in Florida for taking hyper partisan stances on issues, and her penchant for publicity. She is likely to be a prominent public-facing figure during the trial. AFP/Getty All the president's lawyers: The team fighting Trump's impeachment Pat Cipollone Cipollone is the White House counsel, and leading the president's defence team. Getty All the president's lawyers: The team fighting Trump's impeachment Rudy Giuliani While not officially named as one of the president's impeachment lawyers, it is hard to ignore Giuliani's outsized role in this process. The former mayor of New York has been making headlines for months as he defends his client, and for his apparent role in the effort to compel Ukraine to launch the investigation into Joe Biden. We'll see how he figures in the actual trial, which he has said he would like to be a part of. Reuters

Mr Trump’s impeachment follows after his apparent efforts to coerce the Ukrainian government into launching such an investigation into Mr Biden and his family, which he allegedly attempted to force by using a White House visit and US military aid as leverage.

Given his apparent targeting, Mr Biden and his family have been inextricably tied to the claims against Mr Trump, even as the former vice president has maintained that he did nothing wrong during his interactions with Ukraine.

Mr Biden is facing an uncertain path to that nomination, having found stiff competition from the likes of Bernie Sanders, Pete Buttigieg and Elizabeth Warren.

His standing at the top of the polls has diminished recently, and finds himself in second place among averages of national polls in Iowa, which will hold its caucuses next week.