TORONTO -- With polls suggesting a tight race for the White House in November, activists and partisans are hoping a largely untapped group of millions of potential voters, expat Americans living in Canada and elsewhere, can tip the scales in favour of Republican candidate Donald Trump or his Democrat rival, Hillary Clinton.

Their voices could be particularly crucial in swing states such as Florida, where the outcome could hinge on a relative handful of votes.

Accurate figures are impossible to come by, but more than eight million American citizens are thought to live outside the United States with the Canadian diaspora among the largest. Estimates range from hundreds of thousands to more than one million of them in Canada.

For Molly Halpin, who like her three siblings was born and raised in Canada but is also an American by virtue of her mother's citizenship, this is the first U.S. election in which she is eligible to cast a ballot.

"I feel like as a citizen I should exercise my right and ability to vote," Halpin, 20, a student in Ottawa, said Monday. "Also because the thought of Trump being elected is scary."

At the same time, she said, she gave up on a registration process she found confusing and time consuming.

Halpin is exactly the kind of potential voter a new anti-Trump campaign spearheaded by the online activist network Avaaz is trying to reach. The group's online tool aims to ease the pain of registration. It then pushes voters to cast absentee ballots ahead of a deadline that varies by state from later this month to late in October.

Avaaz, which pegs its global membership at the 44 million participants in one of its previous campaigns or petitions, says two million people have visited its website just days into its launch.

"This is really the first of its kind in a global get-out-the vote effort for Americans overseas," Emma Ruby-Sachs, Avaaz deputy director, said from Chicago. "Donald Trump is a global threat. People are terrified. This is something concrete we can do to help stop Trump."

Not everyone sharing the tool at https://secure.avaaz.org/en/globalvote50/ is necessarily anti-Trump, Ruby-Sachs said, but allowing people to express their opinion in an election likely to have global ripples is a "service to the world."

Mark Feigenbaum, 47, of Thornhill, Ont., has voted in most presidential elections since moving to Canada in the 1990s. The lawyer and cross-border tax specialist said what happens in Washington affects all Americans no matter where they live, and U.S. policies do have an impact on Canada.

"This is a get-out-the-vote kind of election," said Feigenbaum, who is chairman of Republicans Overseas in Canada. "It's going to be a tighter election than people think."

Nevertheless, he said the group no longer feels a pressing need to campaign actively to encourage voting given changes in technology.

"The old days, you used to have the booths or you had parties to disseminate information," Feigenbaum said. "Now, it's so easy for people to just go online."

In a statement from Ottawa, Bruce Heyman, the U.S. ambassador to Canada, said the embassy and consulates in Canada have been using social media campaigns and education sessions aimed at expat voters, with Sept. 26 to Oct. 3 designated as absentee voting week.

"I encourage all American citizens residing in Canada to vote," Heyman said. "Voting rules can vary by state, so if you have questions about eligibility or procedures for voting from abroad, there is an important resource you should know: the federal voting assistance program accessible at www.fvap.gov."

Some Americans in Canada, however, say they prefer to stay under the radar because of a crackdown by U.S. authorities on collecting taxes from expats. They worry registering to vote could raise red flags. Feigenbaum, however, said he didn't believe there was any connection, given that voting generally requires registering with a state rather than federally.