DES MOINES — Returning to the campaign trail after Christmas, former Vice President Joseph R. Biden Jr. on Friday stood by his comments that he would not comply with a subpoena to testify at President Trump’s impeachment trial in the Senate.
In a meeting with the editorial board of The Des Moines Register, whose endorsement in the Iowa caucuses is coveted by presidential hopefuls, Mr. Biden argued that complying with a subpoena and testifying would essentially allow Mr. Trump to succeed in shifting attention onto Mr. Biden and away from the president’s own actions.
“The reason I wouldn’t is because it’s all designed to deal with Trump doing what he’s done his whole life: trying to take the focus off him,” Mr. Biden told the newspaper. “The issue is not what I did.”
“This is all about a diversion,” Mr. Biden added. “And we play his game all the time. He’s done it his whole career.”
Mr. Biden met with The Register at the beginning of a two-day visit to Iowa. He boarded his “No Malarkey” campaign bus later Friday and headed to Williamsburg for an event there. Afterward, he stopped by a party at the home of the mayor of Coralville to watch Iowa play Southern California in the Holiday Bowl.
Mr. Biden had previously said that he would not comply with a subpoena to testify at the impeachment trial. Asked Friday about that stance, he said, “The grounds for them to call me would be overwhelmingly specious. But, so, I don’t anticipate that happening anyway.”
Mr. Biden raised the scenario of voluntarily appearing at the Senate trial and explained why he did not view that as a good idea.
“What are you going to cover?” he asked. “You’re going to cover, for three weeks, anything I said. And he’s going to get away.”
The House impeached Mr. Trump last week for abusing his power and obstructing Congress in connection with a campaign to pressure Ukraine to investigate his political rivals, including Mr. Biden and his son Hunter Biden. Since then, Speaker Nancy Pelosi of California has been in a standoff with Senator Mitch McConnell of Kentucky, the majority leader, over whether Democrats will be able to call Trump administration witnesses at a Senate trial.
“I think Nancy Pelosi has done a remarkable job so far in a difficult situation,” Mr. Biden told reporters on his campaign bus later Friday. “I have confidence in her.”
But Mr. Trump and his Republican allies have sought to turn the tables by threatening to call Democrats, including the Bidens, to testify. That could allow Mr. Trump to amplify the same unfounded accusations against the Bidens that he was trying to get the Ukrainian president to agree to investigate in their July 25 phone call.
“We will have Schiff, the Bidens, Pelosi and many more testify, and will reveal, for the first time, how corrupt our system really is,” Mr. Trump tweeted this month before his impeachment, referring to Representative Adam B. Schiff of California, the chairman of the House Intelligence Committee.
The Senate, which is controlled by Republicans, could have difficulty calling Mr. Biden to testify, as some moderate party members might balk at the idea. The party holds 53 seats in the chamber and would need 51 votes to compel the former vice president to appear.
There is no evidence that the elder Mr. Biden, while serving as vice president, improperly intervened in Ukraine to benefit his son. But Hunter Biden was a board member of a Ukrainian energy company while his father worked on Ukraine policy under the Obama administration, a connection that some administration officials viewed as problematic.
On another front in the 2020 campaign on Friday, Senator Elizabeth Warren’s campaign disclosed in a fund-raising email that she had raised just over $17 million since Oct. 1, lagging her fund-raising pace from the third quarter of the year, when she raised $24.6 million.
“We’re only days away from the biggest fund-raising deadline of the year, and we’re at risk of missing our $20 million goal,” her campaign website said.
Ms. Warren, of Massachusetts, is working to reinvigorate her campaign in Iowa after her national polling numbers plateaued in recent weeks. She is scheduled to hold several events in the state over the weekend.
Mayor Pete Buttigieg of South Bend, Ind., who is seen as a front-runner in Iowa, is also campaigning in the state over the next three days.