The impeachment trial of President Trump is underway. Democrats have the rest of this week to establish their arguments for Trump’s removal from office. But the Democrats’ case thus far has focused less on the charges against Trump and more on the witnesses who could justify them.

Senate Democrats want to subpoena several White House witnesses the House didn’t feel it had to hear from, including former national security adviser John Bolton and acting chief of staff Mick Mulvaney. Senate Majority Leader Mitch McConnell will not hold a vote on whether to call these witnesses until after both parties have presented their opening statements. In response, the Democrats have accused McConnell of staging a “cover-up.”