(Reuters) - Bernie Sanders scrapped Iowa campaign appearances, Amy Klobuchar sent campaign representatives to “hot dish” dinners and Elizabeth Warren planned a remote video speech as the Democratic U.S. senators running for president got stuck in Washington for Donald Trump’s impeachment trial.

FILE PHOTO: Democratic 2020 U.S. presidential candidate and U.S. Senator Bernie Sanders (I-VT) speaks during a campaign event in Des Moines, Iowa, U.S., January 20, 2020. REUTERS/Shannon Stapleton

Sanders’ campaign was the first to reschedule events, announcing on Tuesday that progressive firebrand U.S. Representative Alexandria Ocasio-Cortez, known as AOC, would replace him at two rallies in the crucial early nominating state of Iowa while he serves as a juror during the Republican president’s trial in the Senate.

All four Democratic senators running for their party’s nomination to unseat Trump in November’s election - including Michael Bennet of Colorado - must now divert their efforts from the campaign trail for six-day workweeks during the proceedings.

Each is trying to offset the wrinkle in plans by deploying prominent supporters and scheduling intense weekend trips ahead of the Feb. 3 Iowa caucuses, where retail politicking helps motivate voters to go out on a frigid winter evening to stand up for a candidate.

“Some of you are upset because you should be in Iowa now,” Trump’s White House lawyer, Pat Cipollone, said during his opening remarks in the Senate on Tuesday.

Some Iowa political experts say Klobuchar, a senator from Minnesota whose campaign received an unexpected boost over the holiday weekend when she and Warren, a senator from Massachusetts, received endorsements from the New York Times, could suffer more than some others because she is less well-known.

“She has the most to lose by coming off the trail, and the most to gain by staying on it,” said Sue Dvorsky, a former Iowa Democratic Party chair.

‘THIS IS MY JOB’

Klobuchar announced on Tuesday a dozen events to be held by representatives in coming days in Iowa and New Hampshire, including “hot dish” dinners featuring casseroles and appearances by lawmakers or her daughter in the two states.

“I’m going to be doing tele-town halls, and we’ve got my daughter there (in Iowa) right now, my husband is there, we’ve got the – are you ready for this, big celebrity - gold-medal coach of the U.S. curling team – he is there for me,” Klobuchar told reporters during a break in Tuesday night’s impeachment proceedings.

“This is my job. I have to go do this. I need other people to run for me right now, and make my case,” Klobuchar said “That’s what grassroots politics are.”

The proceedings in the Republican-controlled Senate could take weeks, easily stretching into February.

Warren plans to appear at an event in Iowa on Sunday, when the impeachment trial will not be in session. She has scheduled a video appearance before a Las Vegas labor group on Saturday, as well as numerous events anchored by supporters including former U.S. Secretary of Housing and Urban Development Julian Castro, a former candidate who now endorses her.

Trump is charged by the Democratic-controlled House of Representatives with abusing the powers of his office when he asked Ukraine to investigate Democratic political rival, former Vice President Joe Biden, and obstructing a congressional inquiry into his conduct.

Candidates who are not in the Senate - including Biden and former South Bend, Indiana, Mayor Pete Buttigieg - will be able to keep campaigning as usual.

Buttigieg will hold five events across Iowa before he heads to Washington and South Carolina later in the week.

Biden and his wife, Jill, were set to participate in nine scheduled events in Iowa, starting on Tuesday.