FRANCOIS FILLON, 62
Fillon won the conservative nomination in November. He's campaigning on promises of drastic free-market reforms, a hard line on immigration and Islam, support for traditional family values and friendlier ties with Russia's Vladimir Putin.
Allegations that his wife, Penelope, held a fake but handsomely paid job as a parliamentary aide disrupted Fillon's campaign during the last week. Polls suggest his biggest obstacle to advancing in the general election may be far-right leader Marine Le Pen.
BENOIT HAMON, 49
Comparatively inexperienced, Hamon was chosen as the Socialist nominee on Sunday, defeating former Prime Minister Manuel Valls in a primary runoff.
He is a former junior minister and briefly served as education minister under President Francois Hollande. Hamon then rebelled against Hollande's shift toward more business friendly policies and left the government in 2014. His signature proposal is to give a "universal income" of 750 euros ($800) gradually to all adults.
The Socialist candidate is now squeezed between far-left and centrist rivals.