A lot of people who are worried about the future of NATO and the European Union are very concerned about how National Front candidate Marine Le Pen might do in Sunday's French presidential election, said Fox News contributor Marie Harf during a Friday appearance on "Tucker Carlson Tonight."

French people are having a conversation about how to confront terrorism and homegrown radicalism, said Harf, who served under former Secretary of State John Kerry in the Obama administration

"Marine Le Pen is from a very far-right party that has long been shunned in France, which has newfound popularity today," said Harf, who added that Le Pen's policies on immigration and secularism earned her that designation.

Le Pen takes all of these issues to the farthest possible—she has at times called for complete shutdown of immigration and has flirted with leaving the European Union and NATO, added Harf.

"The EU hasn’t been perfect. In the wake of two awful World Wars, [the EU and NATO] helped keep Europe free and at peace," said Harf.

With just a day until voting begins, polls have shown a wide range of possible outcomes. If no candidate earns a majority of votes Sunday, the top two will face each other in a runoff.

"This election could have an impact on the future of Europe," Harf said.