An emboldened Donald Trump celebrated his acquittal in the Senate impeachment trial at a campaign rally in New Hampshire, where he hoped his presence would rattle his Democratic opponents on the eve of the state’s first-in-the-nation primaries.

While the Democratic candidates tore into the president at rallies and events across New Hampshire, Trump fired up thousands of his most ardent supporters at the Monday night rally, his first since the Senate cleared him of abuse of power and obstruction of Congress.

“Our good Republicans in the United States Senate voted to reject the outrageous partisan impeachment hoax, and to issue a full, complete and absolute total acquittal,” Trump thundered to a packed arena in downtown Manchester. “It wasn’t even close!”

Trump tweeted before the rally that he hoped to “shake up the Dems a little bit” as they face a competitive contest, in which Bernie Sanders leads the field in many surveys. The New Hampshire primary has always played an outsized role in the presidential nomination process, but it has taken on a heightened significance following the disastrous failure of the Iowa caucuses to produce a clear winner.

Trump delighted in the debacle, playfully asking the crowd if anyone knew who had won the Democratic caucuses. “(“Nobody knows. Flip a coin!” he said.)

He added later: “The Democrat party wants to run your healthcare but they can’t even run a caucus in Iowa.”

As the Democratic hopefuls crisscrossed the state, Trump supporters came from across the region, braving rain and snow, to attend the rally in Manchester, a one-time manufacturing city of 110,000 people. The line to enter the arena snaked around the arena for several blocks; those at the front had arrived more than 24 hours in advance.

Inside the arena, concession stands sold cotton candy, popcorn and Dippin’ Dots to people in red Make America Great Again hats and pink Women for Trump T-shirts.

Supporters at the Trump rally in New Hampshire. Photograph: Justin Lane/EPA

Trump’s hour-long speech reprised some of his most incendiary remarks, including the claim that undocumented immigrants entering the country are “murderers, rapists and some other things”.

But he also made fresh references. He lashed out at the House speaker, Nancy Pelosi, for her behavior during his State of the Union speech last week when she tore up a copy of his remarks after he finished.

“I’m speaking and a woman is mumbling terribly behind me. Angry – there was a little anger back there,” Trump complained. “We’re the ones that should be angry!” The arena erupted in a round of “Lock her up!!”, a cry once directed at Hillary Clinton.

​But Trump ​also credited the House speaker for his rising poll numbers. Last week, as the Democratic Iowa caucus collapsed into disarray, ​he recorded his highest ever approval rating in a Gallup poll. (“Thank you, Nancy,” he roared.)​

﻿Unlike the Democrats, Trump faces no real competition in the New Hampshire Republican primary on Tuesday, which four years ago delivered his first primary victory. Only Bill Weld, the former governor of Massachusetts, remains in the race as an alternative for the fast-dwindling faction of Never Trump Republicans.

Noting his lack of opposition in the state’s open primary, Trump repeatedly returned to the prospect of his supporters influencing the result by voting for the Democrat who they believe Trump would have the best chance of defeating. New Hampshire election laws allow independents to cast ballots for either Democrats or Republicans.

“A lot of Republicans tomorrow will vote for the weakest candidate possible of the Democrats,” he said. “My only problem is I’m trying to figure out who is the weakest candidate. I think they’re all weak.”

The event on Monday night was part of a strategy to steal the attention from Democrats at a critical moment, as Trump did with a rally in Des Moines on the eve of the Iowa caucuses.

The Trump campaign is using the primary on Tuesday as an opportunity to “flex its organizational muscles” and to reach Republican and independent voters who they hope to win over in November, said spokesman Tim Murtaugh.

Trump lost the state by less than 3,000 votes but his campaign has it firmly in their sights this time around. At the rally, Trump again falsely claimed that he lost the state in 2016 due to voter fraud but said this year should be “a lot different”.

Ray Buckley, the chair of the New Hampshire Democratic Party, called Trump’s visit a “blunder” that will remind voters “why it’s so important to vote” in November 2020. He said the party is investing heavily in the battleground state – which Trump once maligned as a “drug-infested den” on a 2017 call with the leader of Mexico – in case the eventual nominee needs its four electoral votes.

While Trump spoke, the Democrats were spread across the state. Joe Biden held a campaign event across the city at Saint George Greek Orthodox Cathedral; Pete Buttigieg held a rally in Exeter and Bernie Sanders joined the congresswoman Alexandria Ocasio-Cortez and The Strokes for a concert-rally in Durham.

Like Trump, many of his supporters at the event were emboldened by his acquittal in the Senate on Wednesday. Few expressed any doubt about the president’s prospects of being re-elected in November, pointing to a strong economy and the specter of “socialism” if a Democrat wins.

Donald Trump is greeted by his daughter Ivanka Trump at the rally in Manchester. Photograph: Jonathan Ernst/Reuters

“They’ll take our freedom away,” said Joanne Guimond, 64, from Bristol, Connecticut. “We’ll end up like Venezuela.”

Attending a Trump rally is a “bucket list” event for Guimond, who came with her husband Emile, 69.

Not only do they find Trump’s tell-it-like-it-is approach to politics refreshing, but they believe it has helped restore the US to a position of strength at home and abroad.

“Trump’s the only one who’s got balls to do anything for our country,” he said. “He goes to other countries and fights for us. The Democrats? Forget it. He’s the one saving this country.”

Michelle McBride, 58, a New Hampshire state government employee, is confident Trump will win re-election and is encouraged by the state of the economy under his stewardship. The unemployment rate in New Hampshire had already fallen to 2.8% under Barack Obama, but has reduced to 2.6% under Trump.

McBride is alarmed that young people are attracted to the economic policies put forward by the Democratic candidates.

“Today’s youth don’t understand what socialism means,” she said. “And they don’t know what’s going on because there’s no free speech on campuses anymore.”

“The Democratic party is not the John F Kennedy party that we grew up with,” she said ruefully. “I don’t even know what they stand for anymore other than socialism. It’s scary.”