As Democrats push for witness testimony from former national security adviser John Bolton in the impeachment trial of President Donald Trump, at least one Democrat thinks the Senate should hear from another relevant witness: Hunter Biden.

After hearing from the House impeachment managers and Trump's defense team, both of whom referred to Biden heavily in their opening arguments, West Virginia Democratic Sen. Joe Manchin believes partisanship should be put aside in search of the complete truth.

"I think so, I really do. I don't have a problem there because this is why we are where we are," Manchin told MSNBC when asked if Biden was a relevant witness. "Now I think he can clear himself, what I know and what I've heard, but being afraid to put anyone that might have pertinent information is wrong, no matter if you're a Democrat or a Republican."

There is no denying that Biden's activities in Ukraine are central to impeachment. One of the articles of impeachment asserts that Trump abused his power to coerce Ukraine to investigate his political rival, Hunter's father, Joe Biden.

That sought-after investigation concerned Hunter's appointment to the board of Ukrainian energy company Burisma, and whether Joe Biden used his status as vice president and Ukraine point man to protect Hunter and Burisma from anti-corruption investigations.

Trump's defense team argues that seeking such an investigation, even if it carries some personal political benefit to the president, also serves a public interest because there were serious concerns about a potential conflict of interest involving the Bidens.

The House impeachment managers, led by Rep. Adam Schiff (D-Calif.), spent a significant portion of their opening argument claiming that there was no corruption by the Bidens in Ukraine, and that Trump's desire for an investigation was purely for his political benefit.

The Senate will likely vote Friday on whether or not to call new witnesses such as Bolton or Hunter Biden to testify in the trial.