Both have lost points since the broadcast rules came into effect requiring that all 10 candidates be given equal air time on French television and radio, according to Le Monde newspaper. Analysts believe the rules, along with the impression that the result of the first-round vote is already in the bag for Hollande and Sarkozy, may have favoured the fringe candidates.
The most recent research from pollsters Ipsos-Logical Business Consulting for Le Monde, France Télévisions and Radio France, carried out on 13 and 14 April, revealed that Sarkozy had lost two percentage points in a week and Hollande 1.5, putting them tied at 27% each.
Other "small" candidates, as Le Monde describes them, have seen their predicted voting tallies increase. Eva Joly, of the Europe Ecology/Verts party, has gained one percentage point and is at 2.5%. Fringe candidates Philippe Poutou, of the New AntiCapitalist party, and Nathlie Arthaud, of Lutte Ouvrière, have both risen half a percentage point to 1%. Even Jacques Cheminade, a rank outsider who was credited with 0%, has risen half a point, while Nicolas Dupont-Aignan remains at 1%.
Support for those battling for third place appears to have remained stable. Marine Le Pen, of the Front National, has risen half a point to 15.5%, Jean-Luc Mélenchon, of the Front de Gauche, is at 14.5% and François Bayrou has risen slightly to 10%.
Le Monde says that if the poll is confirmed by Sunday's result it will be the first time in modern French history that five candidates have scored more than 10%.
Brice Teinturier, the director general of Ipsos France, said: "The period of strict equality on the amount of speaking time has allowed all the candidates to have the same exposure. It dampens down what we might call the 'privilege of the established candidates', that's to say those that we have seen for a long time and who represent the main political parties.
"As a result the French are discovering the faces and proposals of those who they may not have seen or heard before at the same time as feeling a certain weariness with the 'main candidates' who have been saying what they're saying for a long time."
He added: "The idea, wrong or right, that they [Hollande and Sarkozy] will go through to the second round and that François Hollande will win the second round, allows the voters to support other candidates. That's why we have to keep saying there could be important adjustments made from now until 22 April."
The Ipsos poll predicts that Hollande will win 56% of votes against 44% for Sarkozy in the second round vote on 6 May. It predicts Hollande will get 83% of Mélenchon's first-round votes, and, surprisingly, 37% of the centrist Bayrou's supporters.