Sen. Bernie Sanders Bernie SandersKenosha will be a good bellwether in 2020 Biden's fiscal program: What is the likely market impact? McConnell accuses Democrats of sowing division by 'downplaying progress' on election security MORE (I-Vt.), who is atop polls in Iowa and New Hampshire, said Thursday he is worried about losing valuable time on the campaign trail while he sits through an impeachment trial that could last for weeks.

The Senate spent much of Thursday in a ceremonial session to mark the beginning of President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE's trial, which included all senators present taking an oath administered by Supreme Court Chief Justice John Roberts to uphold impartial justice. Senators then signed an oath book one by one.

Asked later if he’s concerned about how participating in the trial will affect his White House bid, Sanders responded, “Yeah, I am.”

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“I would rather be in Iowa today. There’s a caucus there in 2 1/2 weeks. I’d rather be in New Hampshire and Nevada and so forth. But I swore a constitutional oath as a United States senator to do my job and I’m here to do my job,” he said.

The Iowa caucuses are scheduled for Feb. 3. The New Hampshire primary is eight days later.

Sanders is one of four Democratic senators still running for president, along with Sens. Elizabeth Warren Elizabeth WarrenBiden's fiscal program: What is the likely market impact? Warren, Schumer introduce plan for next president to cancel ,000 in student debt The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon MORE (Mass.), Amy Klobuchar Amy KlobucharThe Hill's Morning Report - Sponsored by The Air Line Pilots Association - White House moves closer to Pelosi on virus relief bill EPA delivers win for ethanol industry angered by waivers to refiners It's time for newspapers to stop endorsing presidential candidates MORE (Minn.) and Michael Bennet Michael Farrand BennetOVERNIGHT ENERGY: House Democrats tee up vote on climate-focused energy bill next week | EPA reappoints controversial leader to air quality advisory committee | Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' Senate Democrats demand White House fire controversial head of public lands agency Next crisis, keep people working and give them raises MORE (Colo.).

Bennet has regularly attended Senate business in recent weeks, but the other candidates have been on the trail.

Despite being about 1,000 miles from the Hawkeye State, Sanders still hit on a couple of his favorite political themes at an impromptu press conference in the Capitol basement Thursday.

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“While we go forward with this impeachment trial, I hope the American people understand that we have not forgotten that in this country, outside of Washington, D.C., today, there are millions of people who are struggling economically, millions of people who cannot afford their prescription drugs or their health care,” he said.

“We’ve got to deal with this impeachment trial but we cannot forget the very serious problems facing the American people,” he added.

Sanders also called on Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE (R-Ky.) to allow new witnesses, such as former national security adviser John Bolton John BoltonDiplomacy with China is good for America The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Pence lauds Harris as 'experienced debater'; Trump, Biden diverge over debate prep DOJ launches probe into Bolton book for possible classified information disclosures MORE, to testify during the impeachment trial.

“When you have a trial, you hear from witnesses. And I hope McConnell will allow those witnesses to testify and give us their version of what happened,” Sanders said.

The Vermont senator missed about half of the Senate’s votes last year as he focused on his presidential campaign.