I see nothing that would lead me to believe that anything that would be said in testimony would sway enough GOP Senators toward conviction. However, at this point, there is the jury of the American People.

Testimony of Mulvaney, Pompeo, Bolton and others would be must see TV and would go a long way in terms of informing more people than a book ever would.

As an example, the televised Watergate Hearings were instrumental in bringing along the public to the point they believed that Nixon had indeed committed impeachable offenses. As noted previously, no amount of incriminating testimony will result in Trump's conviction, but it will portray him as entirely unworthy of reelection to a majority of the electorate. Senator Sam Ervin and John Dean became household names at the time and everybody knew who they were...………..it was THAT big.