Her stunning score in the first round of French presidential elections won her anti-immigrant National Front a place in the Europe-wide march of nationalist—sometimes extremist—parties toward seats of power.
Le Pen's rage will be on millions of voters' minds, both her critics and fans, as they elect a president Sunday.
The same day, Greek citizens, strapped by austerity measures in a nation crushed by debt, could vote in about a dozen lawmakers from the neo-Nazi Golden Dawn.
Bit by bit, far-right parties from the Mediterranean to Scandinavia are gaining momentum among the populace and a foothold in their nations' power structures.
The European debt crisis has added a sharp edge to the mix.
More than two dozen parties around Europe denouncing immigrants—mainly Muslims—as invaders, and calling globalization and the European Union devils in disguise, are gnawing at the political mainstream.
"Islamism is the totalitarianism of religions and globalization is the totalitarianism of trade," Le Pen, who won almost 18 percent of the first round vote, said at a news conference this week. "The nation is the only structure capable" of vanquishing the evil.
The Dutch nationalist Freedom Party of Geert Wilders, the third-largest in the Netherlands' parliament, brought down the minority government last week simply by withdrawing support—an inspiration to Le Pen who cites it as an example of what she and her party could do.
Le Pen's strong strong third place showing in the first round caused conservative President Nicolas Sarkozy to blatantly borrow from her rhetoric in hopes of wooing her voters and saving his job when he faces a runoff Sunday with Socialist Francois Hollande.
Hungary's populist center-right government headed by Prime Minister Viktor Orban is worrying the European Union because of a repressive media law and other restrictive measures. But the country also counts extreme-right Jobbik as its largest opposition party, one with anti-Roma and anti-Semitic overtones.
No one reason can be cited for the rise of populism or the extreme right in a Europe with such varied political, economic and social landscapes and, for former Soviet satellites in central Europe, widely divergent histories.
"There is a need to react to the feeling of the decline of Europe ... Many people, the middle and lower middle classes, feel that their social status has escaped them," said Erwan Lecoeur, a sociologist who studies the far right.
This perceived loss pushes them to reconstruct a new, redefined sense of honor—with the nation as its center and outsiders, including the elite, as the enemy.
Lecoeur cites the term used by renowned turn-of-the-century sociologist Max Weber to refer to whites too poor to own slaves—"the syndrome of poor white trash"—as an apt description of the psychology underlying adhesion to populist parties.
But identifying the parties in question is itself confounding. Are they populist? Nationalist? Extreme right? That depends. They come in all shades.
Anders Behring Breivik, the fanatic extremist who killed 77 people in a July bombing and shooting rampage, was a member of the Progress Party in Norway for seven years, until 2006. The anti-immigration Progress is Norway's biggest opposition party, with 41 of 169 parliamentary seats. Yet it is more moderate than many of its European counterparts and thinks of itself as conservative.
Few parties wish to be referred to as extreme right, which conjures up images of Hitler or the rabble of jack-booted neo-Nazis now being kept at a distance by parties like the National Front.
The varying degrees of extremism and the very nationalism these parties espouse have thus far prevented any meaningful alliances between Europe's far-right groups.
Le Pen contends the neo-Nazi label doesn't suit her and is used to discredit her party, although her National Front, founded in 1972 by her father Jean-Marie Le Pen—convicted numerous times of racism and anti-Semitism—has long been described that way. Experts say the party is deeply anchored in extreme-right ideology.
Le Pen prefers to describe her party as patriotic and nationalist and says she can live with the term "populist," increasingly used to describe Europe's far-right parties.
The National Front under Marine Le Pen, party leader since January 2011, embodies the new far-right, out to prove that immigrants are stealing jobs, multiculturalism is sapping national identities and Europe is severing nations from their souls.
Le Pen and Wilders of the Netherlands are the most visible symbols of the rise of the European far-right. Both are outspoken and charismatic in their bids to bring change.
Le Pen hopes to pierce France's power structure, converting her first round score—a record for her party—into seats in parliament in June elections. Her short-term dream is to become the chief of the French opposition under a leftist president.
Wilders' Freedom Party, which is anti-EU, anti-Muslim and pro-Israel, already has. It won 25 of 150 parliamentary seats in 2010 elections. This week, Wilders launched his English-language autobiography, "Marked for Death, Islam's War Against the West and Me," with a trip to the United States.
Another Freedom Party, this one in Austria, holds 34 of 183 parliamentary seats and polls second in opinion polls, just behind the Social Democrats, one of two parties in the governing coalition. Like France's National Front, it has—under new leader Heinz-Christian Strache—pulled the curtains on its anti-Semitic bent to exploit fears of Islamist domination and the EU.
The Nordic countries each count populist parties opposed to immigration, and the Danish People's Party, Denmark's third largest, pushed the government to adopt some of Europe's strictest immigration laws.
Europe's debt crisis has been fodder for anti-EU parties. Marine Le Pen, like others blaming the euro currency for her country's ills, says, "I knew it would take us into the abyss." She wants a return to the franc.
There is real concern that Europe's debt plight will further stoke dormant tensions.
The Council of Europe's Commission Against Racism and Intolerance warned in its annual report issued Thursday of a rise in intolerance of immigrants and minority groups like the Roma, or Gypsies, due to scarce job opportunities and welfare cuts.
"Xenophobic rhetoric is now part of mainstream debate," the body said after country visits last year. "Resistance to racism is essential to preserve Europe's future," said Jeno Kaltenbach, chairman of the commission.
Far-right parties often advance in small steps, pressuring governments to align laws to fit their populist ideology. Others trumpet their message inside parliament with hopes of finding a place in the mainstream right.
"There is a very strong possibility of contamination of the classic parliamentary right," said Nicolas Lebourg, an expert on the extreme right at the University of Perpignan.
Le Pen herself has said she sees her role as undermining the traditional right so she can eventually embody it.
"You only need to be a spoiler to have an enormous weight," she said. "This victory is inevitable, like that of others in Europe who defend the nation."
Whether the far-right can win real power—for example, running a major European city—is far from certain. But a party need not be in power to do severe damage as it fans social tensions.
"Europe today is a dry prairie waiting for someone to light a match," Lebourg said.
Toby Sterling in Amsterdam, Karl Ritter in Stockholm, George Jahn in Vienna, Juergen Baetz in Berlin, Sylvia Hui in London contributed to this report.