With his Senate trial to begin in earnest next week, President Trump has added some high-profile lawyers to his legal team, including Harvard law professor emeritus Alan Dershowitz and former independent counsel Kenneth W. Starr.

Word of the new firepower came as House impeachment managers and Trump’s attorneys scrambled to produce legal briefs ahead of the Senate’s return Tuesday after the holiday weekend.

The Senate trial opened Thursday amid new allegations about Trump’s dealings with Ukraine, including an assertion from Lev Parnas, a former associate of Trump’s personal attorney Rudolph W. Giuliani, that Trump knew of Parnas’s role in the effort to dig up dirt in Ukraine that could benefit the president politically.

The impeachment charges center on the allegation that Trump withheld military aid and a White House meeting to pressure Ukraine to investigate his political rivals, including former vice president Joe Biden and his son Hunter Biden.

●Senate GOP hopes for a drama-free impeachment trial while bracing for Trump and his legal team.

●The Senate trial will shape the president’s legacy and also that of his Republican Party.

●Trump hotel’s mix of GOP insiders and hangers-on helped give rise to impeachment episodes.

Late Friday, House Democrats released text messages between Lev Parnas and Robert Hyde that indicate a third, unidentified individual was tracking the movements of former U.S. Ambassador to Ukraine Marie Yovanovitch.