While polls before the hearings showed that 49 percent favored impeachment versus 47 percent who opposed it, a survey by Yahoo News and YouGov at the end of the hearings found support for impeachment at 48 percent and opposition at 45 percent. Other polls may eventually show movement but, at first blush, the drama of hearing the evidence presented out loud by real witnesses with evident credibility did not noticeably shift the overall dynamics.
Democrats and Republicans alike privately agreed that it looked unlikely that even a single Republican would vote for impeachment when it reaches the House floor. In the Senate, Republican strategists said they believed they might lose two senators — Susan Collins of Maine and Lisa Murkowski of Alaska — while Democratic strategists said they also might lose two — Joe Manchin III of West Virginia and Kyrsten Sinema of Arizona.
“We’ve just had this partisan divide ever since the Clinton years,” said former Representative Barbara J. Comstock, Republican of Virginia. “Whether it was Supreme Court nominations or this, it’s just become a team sport, shirts and skins, no matter what the issues are.”
Steve Elmendorf, the top aide to the House Democratic leader when Mr. Clinton was impeached, agreed that lawmakers appear locked into their positions. “Except,” he cautioned, “we are in the Trump show, where anything can happen. Two months ago, we did not think he was going to be impeached over a phone call we knew little about.”
Among the wild cards that could still change the dynamics might be testimony by some of the key witnesses who so far have refused to talk, including John R. Bolton, the former national security adviser who opposed the pressure campaign and is waiting for a court ruling on whether he should appear.
Mr. Trump has long argued that an impeachment battle would help him politically by galvanizing his base against the elites trying to invalidate the 2016 election. While he has refused to provide testimony or documents to the House, arguing that the process is rigged against him, he is taking his case instead to evening rallies in sports arenas filled with supporters.
Mr. Trump and his allies took heart from a Marquette University Law School poll showing him with small leads against each of the Democratic front-runners among voters in Wisconsin, one of the most critical battleground states for 2020. That poll, taken during the first week of hearings, showed that support for impeachment in the state had slipped by four percentage points to 40 percent.