Two years after the presidential election was decided by 80,000 votes in three states, millions of Americans are heading to the polls to cast a ballot in pivotal midterm elections that will determine control of Congress and the future of President Donald Trump's agenda.

As canvassers tell voters that every ballot counts, voting rights advocates worry that new laws, controversial policies, and confusion could keep voters from exercising their democratic rights.

"We’ve seen an unfortunate number of suppressive activity for this election cycle," said Myrna Pérez, deputy director at the Brennan Center for Justice, a nonpartisan law and policy institute.

Pérez urged people to still go out and vote despite any troubles: "Do not be deterred," she told NBC News. "Your vote is your voice."

Here’s where voting issues have already arisen or could arise, and what's being done about it.

New laws in eight states

The 2018 election will mark the debut of new voter ID requirements in Arkansas, Iowa, Missouri, North Dakota and Texas, with other voting law changes being implemented for the first time this year in Indiana, Georgia, Iowa, New Hampshire, according to the Brennan Center. New laws often prompt confusion.

In North Dakota, a voter ID law is forcing an estimated 5,000 Native Americans to get new ID cards that list street addresses — not the post office boxes many had been using for years — in order to vote.

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Even less recent laws can cause confusion: The American Civil Liberties Union of Michigan is urging election clerks across the state to help voters understand that photo ID is not required to place a ballot after voters reported receiving information that they would need such ID to vote. Those without voter ID can sign a form attesting that they do not have photo ID or do not have it with them, the ACLU told local outlets.

The spate of new laws, which were placed on the books almost exclusively in red states, come despite the lack of proof that voter impersonation is anything more than a minuscule problem.

Justin Levitt, a professor at Loyola Law School and former Department of Justice official who has been studying the issue for years, said he found just 45 credible cases of voter impersonation between 2000 and 2018, a period during which more than a billion votes were cast.

So why the insistence on new voter ID requirements?

"Some of it might be perceived political advantage (as an issue), some of it might be perceived electoral advantage, some of it might be animus toward populations without the required kind of ID," Levitt said in an email to NBC News. "Some of it might be lack of understanding of the injuries caused by requirements that are difficult for real eligible voters to meet, and some of it might be lack of empathy for those injuries. Or some combination of the above."

Georgia voter registrations — and their signatures — on the line

More than 50,000 Georgia voter registrations were put on hold over the state’s “exact match” protocol, an Associated Press investigation found in October. The policy mandates that voting records match other government records perfectly, and can keep voters from the polls if a misplaced hyphen or typo appears. The policies hit minorities hard: the AP investigation found that 70 percent of the people put in limbo were African-American.

Civil rights groups sued Georgia Secretary of State Brian Kemp, the Republican candidate in the state's hotly contested gubernatorial race and the state's top elections official, over the exact match policy. A federal judge also barred Georgia officials from tossing absentee ballots where the voter's signature doesn’t match exactly. Voters must be given a chance to rectify the discrepancy, a judge said.

On Friday, a federal judge also ruled against Kemp in a suit over some 3,000 voters flagged as potential noncitizens, telling the state to establish procedures that guarantee those voters a ballot if they can prove their citizenship.

Big purges in four states

West Virginia, Florida, Georgia, and North Carolina are purging voters aggressively, the Brennan Center has reported, raising concerns that eligible voters could be accidentally purged. While purging out-of-date registrations from the polls is a normal part of election administration, voting rights advocates say purges must be done precisely.

West Virginia's secretary of state announced in September that it had purged more than 100,000 voters from its voter rolls, which now has 1.27 million voters.

Purged voters given the right to vote in Ohio

After the Supreme Court gave the all-clear to Ohio's voter purge process — which boots voters who don’t cast ballots for three federal elections and ignore a confirmation notice from election officials — voting rights advocates took the state to court over purge confirmation notices, which they argued were too vague. A judge ruled this week that purged voters could still vote, while advocates continued to challenge the wording of the confirmation notice.

Meanwhile in Gotham

The New York City Campaign Finance Board may have unwittingly sabotaged its own get out the vote drive by stating falsely — in a midterm elections guide sent to millions of residents — that paroled felons are barred from voting.

The language in our Voter Guide was not updated to reflect the executive order restoring voting rights to most parolees in New York. We regret the error and any confusion that this has caused. pic.twitter.com/im1TrQhZKw — NYC Votes (@NYCVotes) October 31, 2018

The board apologized for the mistake and quickly made the fix online. But it was too late to fix the snafu on page two of the 32-page document that was mailed to registered voters in mid-October.