WASHINGTON — Senate Republicans indicated on Monday that they would not seek to summarily dismiss the impeachment charges against President Trump, proceeding instead to a trial with arguments and the possibility of calling witnesses that could begin as soon as Wednesday.
Dismissal was always a long shot given Republicans’ narrow control of the Senate, but it was the subject of renewed discussion after Mr. Trump said on Sunday that he liked the idea put forward by some conservatives as a way to deny the House’s case the legitimacy of a trial. Other Republicans had signed on to a resolution that would have dismissed the House’s impeachment articles if they were not promptly brought to trial.
In interviews, rank-and-file senators and party leaders made clear on Monday that even if they wanted to pursue dismissal, the votes simply were not there to succeed — at least not at the outset of the trial. They did not rule out considering a motion to dismiss the charges of abuse of power and obstruction of Congress after opening arguments from both sides.
“Our members generally are not interested in a motion to dismiss,” said Senator Roy Blunt of Missouri, a top Republican leader. “They think both sides need to be heard. They believe the president needs to be heard for the first time in a fair setting.”
In the House on Monday, Democrats leaving meetings with Speaker Nancy Pelosi indicated that the chamber was most likely to vote on Wednesday to name lawmakers to prosecute the case and to send its two impeachment charges to the Senate.
Behind the scenes, aides in the House and Senate were carefully choreographing the next steps, and some Democrats in the House cautioned that a vote could still slip to Thursday, as the Senate seeks to deal with a pending War Powers Resolution and Mr. Trump’s new trade agreement with Canada and Mexico. In any case, a trial would not be expected to start in earnest, with opening oral arguments, until next week.
Asked when Democrats would name their impeachment prosecutors, or managers, Representative Steny H. Hoyer of Maryland, Ms. Pelosi’s No. 2, said that it “could be Wednesday.” He pointed out that the Senate would have “practical problems” if the House moved sooner, including missing three senators who are expected to take part in Tuesday night’s Democratic presidential debate.
For Republican leaders, the decision to bypass an attempt at dismissal reflected competing interests as they sought to navigate a complex constitutional process with little precedent.
As the trial has approached, Senator Mitch McConnell, Republican of Kentucky and the majority leader, has seemed increasingly keen to keep it as tightly controlled and speedy as possible. He is wary of what could happen if Democrats succeed in picking off moderate Republican senators to form a majority able to call witnesses and prolong the proceeding.
But he also wants to ensure that those same moderate senators — several of whom are up this fall for re-election in swing states — can credibly claim to voters that they took their constitutional duties seriously.
One of those lawmakers, Senator Susan Collins of Maine, made clear on Monday that she was not interested in a dismissal motion now, or most likely ever.
“I would anticipate voting against a motion to dismiss, as opposed to going through the whole process and going to final arguments and having a vote on each article of impeachment,” she told reporters.
Democrats offered a motion to dismiss the charges against President Bill Clinton in his 1999 impeachment trial after the House and White House had made their opening arguments. But the resolution failed and the trial lasted several more weeks before senators ultimately voted to acquit Mr. Clinton on both charges against him.
Mr. Trump endorsed the idea of outright dismissal on Sunday, though his own views have oscillated wildly in recent weeks. On Twitter, the president warned that holding a full trial “gives the partisan Democrat Witch Hunt credibility that it otherwise does not have.”
Ms. Collins was not the only Republican who spoke out against the idea on Monday.
“At this stage, the allegations that have been made are serious and deserve to be given consideration with the arguments for and against,” said Senator Mitt Romney, Republican of Utah.
And Senator Lamar Alexander of Tennessee, who will not seek re-election in 2020, said he would vote against an immediate dismissal if it were proposed.
“We’re taking an oath to be impartial,” he said, “and that to me means we have a constitutional duty to hear the case, ask our questions and then decide whether we want additional evidence in terms of documents or witnesses.”
All three senators, plus Senator Lisa Murkowski of Alaska, also said Monday that they were pushing Mr. McConnell to allow votes on calling additional witnesses and evidence after opening arguments, though only Mr. Romney stated he would outright support calling witnesses.
Catie Edmondson, Michael D. Shear and Sheryl Gay Stolberg contributed reporting.