Democratic candidates bolt Sunday across Iowa, where no handshake or pit stop is too insignificant one day ahead of the state’s presidential nominating process, which is the first in the nation.

Iowa has traditionally served as a vital launching point – or burial ground – for presidential campaigns. However, Monday’s crunch vote has created an air of suspense, with no clear frontrunner.

Senator Bernie Sanders holds only a narrow lead over former vice-president Joe Biden, among the field of several candidates feverishly crisscrossing the rural state.

Three of the leading candidates seized on a brief break from their duties as jurors in the Senate impeachment trial of President Donald Trump in Washington to rush to Iowa for a flurry of last-minute events.

The senators – Sanders, progressive Elizabeth Warren and moderate Amy Klobuchar – each held a handful of events on Saturday.

The impeachment trial – only the third in US history – created an unprecedented situation by limiting the senators’ ability to campaign in Iowa in the closing days before the state’s presidential caucuses.

Sanders, Warren and Klobuchar have to return to Washington on Monday, along with Senator Michael Bennet who trails badly in the polls, for the trial’s resumption.

Senate leaders have scheduled a vote for Wednesday that appears virtually certain to end in Trump’s acquittal on the impeachment charges of abuse of power and contempt of Congress.

Eight of the 11 Democrats still in the race were in Iowa on Saturday.

A good result can propel a candidate to new victories in the states that follow, starting with tiny New Hampshire eight days later.

Sanders, at 78 the oldest Democratic candidate, has seen his candidacy buoyed by enthusiastic support among young voters.

His staff organised concerts at his weekend rallies.

“We must defeat the most dangerous president in the modern history of America,” the Vermont senator told a crowd of several thousand in Cedar Rapids.

“Monday night in Iowa it all begins,” he said.

On Monday evening, at 7pm (0100 GMT Tuesday), the state’s more than 600,000 registered Democrats are invited to take part in caucuses at about 1,700 venues – schools, theatres, churches – to publicly express their choice by standing under one candidate’s banner.