Temporary home to thousands of migrants trying to reach Britain, the French city of Calais is a major battlefield for presidential candidates who are seizing on fears of immigration in campaigning for spring elections — and following in the footsteps of far-right leader Marine Le Pen. Former President Nicolas Sarkozy, competing in the conservative primary in November, is visiting Calais on Wednesday, where he's expected to pledge to send migrants to a processing center in Britain. Sarkozy will not go to the makeshift camp known as the jungle — instead he will meet security forces in charge of protecting the ferry port and preventing migrants from entering the area. Presidential contender Le Pen, well positioned in polls, has made fighting immigration her longstanding issue. The president of the National Front is campaigning to leave the EU and its visa-free zone, which would allow France to reinstate controls at national borders. Sarkozy's rivals for the conservative nomination have also visited Calais, and President Francois Hollande — who is eying a re-election bid but has not formally declared his candidacy — is considering going to Calais next week. The "jungle" and its inhabitants from Africa, the Middle East and beyond are a thorn in the side of the Socialist government, the symbol of its failure to find effective responses to Europe's migrant crisis. French conservative politicians argue that British authorities should be responsible for dealing with people who want to demand asylum in the UK. The French want to renegotiate a 2003 treaty that effectively puts the British border in Calais, leaving French authorities to police migrants trying to cross the Channel. Sarkozy signed the treaty himself as interior minister. Now he wants to maintain border controls on the French territory, because the UK is not part of Europe's free-travel zone, but also wants to send migrants to a center on the British territory. — AP