Democrats want three consolation prizes out of this process, knowing that they’re destined to lose the trial. Possibly with a bipartisan vote for acquittal.
First prize: Damaging Trump’s chances at reelection. They can tolerate the Senate voting “not guilty” if the electorate, watching these proceedings, votes to “convict” on Election Day. Democrats might even prefer that. If the Senate removed Trump, his ouster would be regarded by Republicans as a travesty calling into question the legitimacy of America’s entire democratic system. If instead the voters remove him in November, eh. That’s elections for you. Dems at least want to wound him now in hopes that the public will deliver the coup de grace this fall.
Second prize: Damaging Susan Collins’s and Cory Gardner’s chances at reelection. Schumer will trade losing this trial for a pick-up of two Republican-held Senate seats in battleground states. Unquestionably he’d trade a “not guilty” verdict for some sort of guarantee of a Democratic Senate majority next year, knowing that that would mean he could block all of Trump’s appointments even if POTUS were to win a second term. Dems will use whatever pro-Trump votes are cast by Collins and Gardner during this process to cast them in their Senate races next fall as hardcore Trump toadies who don’t represent the centrist politics of their home states.