The French conservative presidential candidate, Francois Fillon, has suffered new setbacks in his campaign, with a political ally suspending its support.
The centrist UDI party, with 27 MPs in the lower house of parliament, says a final decision will be made next week.
It follows the revelation that Mr Fillon is facing a formal investigation over a fake job scandal involving his wife. He denies any wrongdoing.
A key aide has also left his campaign.
Foreign affairs spokesman Bruno Le Maire criticised the candidate for breaking his pledge to step aside if he was put under formal investigation.
Mr Fillon says he has been summoned to appear before a judge on 15 March, just two days before the deadline for candidates to submit their final applications.
The first round takes place on 23 April, followed by a run-off on 7 May.
Thursday promises to be a busy day for the election campaign with liberal candidate Emmanuel Macron due to present his programme at a press conference.
'Give the money back!'
The head of the UDI, Jean-Christophe Lagarde, said the party was halting its support and the party leadership would meet next week to decide whether to fully withdraw its backing for Mr Fillon.
While the party has just 27 MPs to the 193 of Mr Fillon's Republicans in the National Assembly, its endorsement would broaden his appeal.
Bruno Le Maire, who stood against Mr Fillon in the Republican primaries, said he could not longer back his party's candidate.
"I believe in keeping your word," he said. "It is vital to the credibility of politics."
But Mr Fillon argued it was up to voters to decide his fate.
"It's not just me that is being assassinated, it's the presidential election," he said in a speech on Wednesday.Media captionFrancois Fillon: "I will take it to the end"
"The voices of millions of votes have been muzzled. The closer we get to the date of the presidential election, the more scandalous it would be to deprive the right and centre of a candidate."
President Francois Hollande later commented that no candidate had the right to bring the legal authorities into disrepute.
The allegations circling around the Fillon family focus mainly on his Welsh-born wife Penelope, who is reportedly also facing an investigation.
The Le Canard Enchaine newspaper alleges she was paid €831,400 (£710,000; $900,000) over several years for working as a parliamentary assistant for Mr Fillon and his successor, but had no parliamentary pass - raising questions over whether she did the work she was paid for.
She was also alleged to have picked up €100,000 for writing a handful of articles for a literary journal.
During a visit to the Paris farm fair later on Wednesday, supporters shouted "Fillon, President!" while others yelled "Thief! Give the money back!"
- More about the Fillon payment inquiry
Race picks up
Opinion polls suggest three other candidates have a chance of passing the first round and reaching the run-off:
- Far-right National Front (FN) leader Marine le Pen, who is also facing allegations that she misused EU funds, a claim she denies. Her proposals include a slash on legal immigration, a deportation of illegal immigrants and a referendum on exiting the EU and euro
- Liberal Emmanuel Macron, from En Marche (Onwards). He is running his first ever election. His programme is expected to include public investments alongside big spending cuts and further reforms to the way people work
- Socialist Benoit Hamon, who proposes a universal monthly payment for all French citizens, regardless of income and the legalisation of cannabis
More on the candidates
Ms Le Pen will deliver a speech on the role of the French state and the economy on Thursday, and Mr Hamon will also visit the Paris farm fair.
In the morning, all of the leading candidates are also expected to speak at a conference on media and communication.