(CNN)Germany's Ursula von der Leyen is on the verge of succeeding Jean-Claude Juncker to become the European Commission's first female president on Tuesday -- if leaders of the 28 EU member states have their way.
Europe's likely next president may need far-right votes to win. Some see that as a 'catastrophic sign'
A long-time ally to German Chancellor Angela Merkel, and the only minister to have served in Merkel's cabinet since she came to power back in 2005, von der Leyen's nomination to replace Juncker was unexpected since she wasn't even a candidate.
"She didn't campaign, she never came out, she didn't take part in any debate," explains Anna Nadibaidze from the policy think tank, Open Europe.
European leaders nominated the German defense minister to lead the Commission after they failed to agree on any of the "Spitzenkandidat" nominees -- who are put forward by European political parties ahead of the EU elections. Von der Leyen beat the original frontrunner for the role -- Dutch socialist Frans Timmermans.
And while her nomination was supported by a majority of EU leaders, it's unclear if she'll receive the same support when 751 Members of the European Parliament vote to approve the appointment on Tuesday.
Von der Leyen, 60, may not receive the majority she requires from parliament, due to critics branding her nomination a "backroom" deal.
"Her nomination is mostly seen as a French-German deal that was done behind closed doors and some people call it a stitch-up," Nadibaidze told CNN.
"That's the danger -- that she might not get accepted specifically because of the process."
Domestically, Nadibaidze says, von der Leyen has faced a lot of criticism, particularly from Merkel's coalition partners -- the Social Democrats (SPD), who are upset that EU leaders ignored the top candidates after days of horse-trading.
"They think she's one of the weakest ministers (and) that she couldn't command the army," Nadibaidze explains. "There was also an article in the German press saying that how the German army is happy to get rid of her."
Born in Brussels and multilingual, there's no denying von der Leyen has a European background -- something, Nadibaidze says, the German has been using to her advantage "when she tries to convince MEPs to vote for her."
She has also followed in the footsteps of her father, Ernst Albrecht, who was a Christian Democratic Union (CDU) politician and a senior European civil servant.
When von der Leyen was grilled by MEPs last Wednesday, as she made her pitch on why lawmakers should vote for her, she switched between German, French and English.
She said it was vital to improve the "competitiveness" of the EU's economy, that Europeans want a "united, strong, open-minded" EU and that the bloc needed to "become more assertive" towards the US.
Von der Leyen also told MEPs that she was fully committed to the goal of carbon neutrality by 2050, but in order to do so the EU needed to be "more ambitious and more bold."
As a member of the center-right Christian Democratic Union (CDU), von der Leyen can rely on the support of allied MEPs from the largest political group in parliament -- the European People's Party (EPP).
Von der Leyen's colleague from the CDU, Gunther Krichbaum, says he's known her for many years, and told CNN he was convinced she would be an excellent president.
"She has always been extremely competent, assertive and reliable, but also always conciliatory," he added.
But when it comes to support from the EU's left-leaning groups -- it's a different story.
The EU's second largest political group, the Progressive Alliance of Socialists and Democrats (S&D) -- which has 154 seats in parliament -- has said it is "deeply unhappy" about von der Leyen's nomination, believing Timmermans "was by far the best-qualified candidate and was the person to deliver the change Europe needs."
The S&D added that "large questions remain" following von der Leyen's grilling last week, and that it was awaiting a reply to a letter outlining that party's key demands before deciding whether it will vote in favor for her or not.
Meanwhile, both the Greens/European Free Alliance (Greens/EFA) group and the Confederal Group of the European United Left -- Nordic Green Left (GUE/NGL) have announced that they would not be supporting her because of her policy vagueness.
Greens/EFA MEP Sven Giegold called von der Leyen "unspecific" on where she stands, with "largely evasive" responses, "rather than clear attitudes and positions."
"The next EU Commission must act harder, not softer, against the breach of European values," Giegold told CNN.
Both groups also said despite von der Leyen telling lawmakers last Wednesday that she supports the EU going carbon neutral by 2050, it was not enough.
Greens/EFA President Ska Keller said in a statement that the group does not see "how change will be possible" with a candidate like her.
If von der Leyen's nomination is approved by MEPs in a secret ballot on Tuesday evening, she'll lead the EU's executive body and provide political guidance to the Commission -- which proposes new laws, manages the EU budget and is responsible for enforcing EU law.