Washington (CNN) Sen. Jeanne Shaheen, D-New Hampshire, plans to send 2020 Democratic presidential candidates a letter Monday, urging them to sign a petition condemning a state law that would require college students to be a permanent resident of the state to vote.

"I am asking every candidate for President to stand up for these students, condemning these tactics and protecting the integrity of New Hampshire's voting process by signing a petition publicly denouncing this voter suppression law," Shaheen, the state's senior senator, writes in a letter she intends to send to all 18 declared candidates Monday morning.

Currently, New Hampshire does not require registered voters to prove residency -- only to prove "domicile."

But the new state law, House Bill 1264, which goes into effect in July, puts the same legal requirements for residents onto "domicile" persons. Those from out-of-state living in New Hampshire, like college students, will have to pay fees to obtain a New Hampshire driver's license and register their vehicles within 60 days of established residency, or after casting a ballot. The Granite State also allows same-day voter registration

In her letter, which CNN obtained ahead of its publication, Shaheen argues that the law effectively creates a "poll tax" for college students.

"They are being disenfranchised by photo ID requirements, arbitrary challenges to residency, and unfounded allegations of fraud," Shaheen writes.

President Donald Trump has claimed, without evidence, that thousands of people were bused from Massachusetts to vote illegally in New Hampshire, which he narrowly lost in the 2016 state primary.

New Hampshire Secretary of State Bill Gardner refuted the President's claim, telling the Boston Globe , "We have never gotten any proof about buses showing up at polling places."

CNN is hosting back-to-back town halls Monday night with five 2020 Democratic candidates in New Hampshire. Sens. Amy Klobuchar of Minnesota, Elizabeth Warren of Massachusetts, Bernie Sanders of Vermont and Kamala Harris of California, as well as South Bend, Indiana, Mayor Pete Buttigieg will appear in the events beginning at 7 p.m. ET.

The presidential hopefuls will field questions directly from students and young New Hampshire Democrats on issues of importance to young voters.

Presidential candidate and former Democratic Rep. Beto O'Rourke weighed in on Sunday.

"Don't need to wait until tomorrow on this," he tweeted. "The law is wrong. It must be overturned. And we must enact a new Voting Rights Act so every person is able to cast their vote, have their voice heard, fully participate in our democracy."

Democratic presidential candidate Sen. Kirsten Gillibrand of New York also spoke out against the law on Sunday.

"Our democracy is strongest when voters have the freedom to head to the ballot box to make their voice heard," she tweeted. "The efforts of @GovChrisSununu to restrict this right for tens of thousands of students is unconscionable. I strongly support efforts to amend and repeal this bill."

Shaheen's push for 2020 Democrats to reject the bill comes as the candidates barnstorm the state ahead of its early presidential primary -- a key to building momentum for their campaigns.

"With the nation's eyes turned toward our first-in-the-nation primary, we have an opportunity to send a clear message to anyone seeking to subvert voting rights," Shaheen writes in her letter. "I hope that you will join me in standing up for all Americans' right to vote."

The chair of the state's Democratic Party called for every presidential hopeful to sign the pledge.

"Every candidate for President campaigning in New Hampshire should sign Senator Shaheen's pledge and commit to protect the right to vote for everyone in the Granite State, especially the young people now threatened by a new voter suppression law that must be condemned and overturned," said New Hampshire Democratic Party Chairman Ray Buckley in a statement provided to CNN.

When HB 1264 was passed last year in the state legislature, the state Supreme Court found in a 3-2 ruling that the bill was constitutional and places "voters and residents on equal footing as New Hampshire citizens," according to the Concord Monitor

After initially questioning the bill's constitutionality, Republican Gov. Chris Sununu signed the measure into law last July following the court's decision.

"House Bill 1264 restores equality and fairness to our elections," Sununu said in a statement, adding, "Finally, every person who votes in New Hampshire will be treated the same. This is the essence of an equal right to vote."

But New Hampshire's Democrats, after taking control of the state House and Senate in the 2018 midterms, have sought to undo HB 1264. The law also faces a legal challenge.

The American Civil Liberties Union, on the behalf of two Dartmouth college students, sued the state's attorney general and secretary of state in February, arguing the law is unconstitutional.