After taking the night to consider the issues at hand, senator Lisa Murkowski announces she will not support a call for further witness testimony.  It appears the primary concern for Murkowski was her ‘yea’ vote creating a 50/50 split; and she anticipates Democrats attempting to manipulate further rules forcing Chief Justice Roberts to be the deciding factor.  Murkowski stated: “I will not stand for nor support that effort.”
Posting to her Facebook Page the Alaska Senator writes:

“I worked for a fair, honest, and transparent process, modeled after the Clinton trial, to provide ample time for both sides to present their cases, ask thoughtful questions, and determine whether we need more.
The House chose to send articles of impeachment that are rushed and flawed. I carefully considered the need for additional witnesses and documents, to cure the shortcomings of its process, but ultimately decided that I will vote against considering motions to subpoena.

Given the partisan nature of this impeachment from the very beginning and throughout, I have come to the conclusion that there will be no fair trial in the Senate. I don’t believe the continuation of this process will change anything. It is sad for me to admit that, as an institution, the Congress has failed.
It has also become clear some of my colleagues intend to further politicize this process, and drag the Supreme Court into the fray, while attacking the Chief Justice. I will not stand for nor support that effort. We have already degraded our institution for partisan political benefit, and I will not enable those who wish to pull down another.
We are sadly at a low point of division in this country.” (link)