Schumer's leverage is limited, though his party can force votes on witnesses once a trial begins. He appears to be counting on public opinion, and political pressure on VULNERABLE Republican incumbents like Susan Collins of Maine, to give Democrats the 51 votes they need.
[...]
Trump, meanwhile, has been hoping the trial will serve as an opportunity for vindication. He continues to talk about PARADING his own witnesses to the chamber, including former Vice President and 2020 Democratic candidate Joe Biden and House Intelligence Committee Chairman Adam Schiff, D-Calif., who led the fact-finding phase of the impeachment investigation.