All it takes is four. That’s the number of Senators that would need to join Democrats in voting to call witnesses at Donald Trump’s impeachment trial. CBS News writes:

Senior White House officials tell CBS News they increasingly believe that at least four Republicans, and likely more, will vote to call witnesses. In addition to Senators Lisa Murkowski of Alaska, Susan Collins of Maine, Mitt Romney of Utah and possibly Cory Gardner of Colorado, the White House also views Rand Paul of Kentucky as a “wild card” and Senator Lamar Alexander of Tennessee as an “institutionalist” who might vote to call witnesses, as one official put it.

Collins said last week she was working with a small group of Senators who were in favor of calling witnesses such as former national security adviser John Bolton.

A poll released on Monday shows why politicians are suddenly warming to the idea. Two-third of Americans polled support Bolton testifying.

Democratic Representatives Adam Schiff and Jerrold Nadler will likely be named House impeachment managers.