A U.S. congressman looking to thwart President Joe Biden, a fellow Democrat, from a second term assailed Biden as weak and unelectable on Saturday as he tried to take advantage of Biden's absence from New Hampshire's first-in-the-nation primary.

Biden is skipping the New Hampshire primary after the Republican-run state refused his demand to give up its first in nation primary spot to South Carolina. But Biden's supporters are mounting a write-in campaign to avoid an embarrassing loss in the state on primary election day on Tuesday.

Congressman Dean Phillips, a wealthy Democrat from Minnesota who is running for president, said during a campaign event in Nashua, New Hampshire, that he hoped to expose what he called Biden's weakness by doing well in Tuesday's voting.

Phillips said a strong showing by him would be getting upwards of 20% or more of the vote - "going from zero to somewhere in the 20s would be pretty awesome, I think."

"Sadly it's going to demonstrate that our incumbent president is unelectable and weak and I think it's going to show this country that there's a candidate here who can actually do here what has been promised for generations," Phillips told reporters after addressing dozens of people at a senior citizen activity center.

He also noted Biden's advanced age, 81.

"If you listen to the voters, people feel he's at a stage of life that makes it incompatible to leading the free world. And the same is true of Donald Trump," said Phillips, 55.

Trump, 77, is the leading Republican candidate. The former president was defeated by Biden in his bid for a second term in 2020.

The Biden re-election campaign did not respond immediately to a request for comment.

The New Hampshire primary on Jan. 23 offers the first at-the-polls gauge of Biden’s political strength this election cycle, and the unprecedented situation will be closely watched amid polls showing him tied with Trump.

A poor showing by Biden against Phillips and self-help author Marianne Williamson would likely fuel concerns that Biden is weak heading into the general election.

Both Phillips and Williamson appeared to have little chance of defeating Biden.

Backers of the write-in campaign are staging events throughout the weekend to educate voters on how to write in Biden's name and generate support for him.

Williamson told several dozen people at an event in Manchester that she also felt Biden was weak and questioned the wisdom of nominating him for a second term just because he beat Trump in 2020.

"To say he beat Trump once and therefore he'll beat him again - for me it's like saying to an actor who's nominated for an Oscar twice. 'He won last time so it's only reasonable to think he'll win this time. Well, it's a different movie," she said. (Reporting by Steve Holland; Editing by Sandra Maler)