Higgins, 70, didn't comment as the painstaking count of ballots continued following Thursday's election. Official results are expected Saturday because of Ireland's complex voting system, which permits voters to rate candidates in order of preference and requires several rounds of counting.
But partial totals of first-preference votes put Higgins in an unassailable lead with more than 40 percent support versus six other candidates. Gallagher was running second with about 22 percent. Former Irish Republican Army commander Martin McGuinness was third, gay rights activist David Norris fourth.
"I'm very happy to be an Irishman under the presidency of Michael D. Higgins," said Norris, who lauded his rival as a political maverick and social liberal who would "speak out on behalf of the marginalized."
Former Foreign Minister Micheal Martin - whose Fianna Fail party was ejected from office by angry voters earlier this year and didn't run a presidential candidate - said Higgins "will make an excellent president and ambassador for Ireland." He praised Higgins' "command of global issues and commitment to human rights."
Higgins is widely known in Ireland simply as "Michael D," befitting his status as one of the country's most liked and instantly recognized politicians. He stands just 5 foot 4, his elfin features complemented with a much-parodied high voice infused with his rural County Clare roots.
Higgins, a former University College Galway lecturer in sociology and politics, is credited as an intellectual heavyweight of Irish politics with three published collections of poetry to his credit and a four-decade record of promoting home-grown arts, literature, film and the native Gaelic language. Unlike other English-only candidates and most of the nation, Higgins spoke the native Irish tongue fluently on the campaign trail.
He also has traveled the world defending left-wing human rights cases. He is one of Ireland's most ardent critics of U.S. foreign policy, particularly in Central America, Iraq and Afghanistan, and of Israel's policies versus the Palestinians.
His socialism came to the fore on the campaign trail as he condemned the get-rich-quick excesses of Ireland's lost Celtic Tiger boom economy, arguing its narcissism and greed left the country mired in debt and unemployment.
Gallagher, an entrepreneur and the star judge on a business-talent TV competition called "Dragon's Den," last week seemed on course to an unlikely victory as he pledged to lead Ireland back to prosperity.
He had a 15-point lead in opinion polls versus Higgins until Monday - when his image imploded during the campaign's last live TV debate.
McGuinness presented evidence that Gallagher had served as a "bagman," a collector of undocumented cash donations, from businessmen to Fianna Fail. Voters in February expelled Fianna Fail from office after the long-dominant party was blamed for leading Ireland to the brink of bankruptcy and an international bailout.
Gallagher, who ran as an independent and downplayed his Fianna Fail background, stumbled as he tried to explain the circumstances of one donation he allegedly collected from a border fuel smuggler. Analysts said that admission linked Gallagher fatally in voters' minds to Fianna Fail's poor ethical record.
Higgins' campaign team seized on their candidate's own reputation for honesty and integrity as a point of contrast. Full-page newspaper ads on election day claimed that the "D" in Higgins' name stood for democracy and decency. It actually stands for Daniel.
A survey published Friday by Irish pollsters RedC said it telephoned 1,100 citizens Thursday after they had cast their ballots and detected a massive flight from Gallagher in the campaign's dying days.
About 38 percent said they had decided whom to support only following that TV debate. Some 28 percent said they had switched support in the past week - and 58 percent of those said they had dumped Gallagher.