"ascendancy as" is a grammatically correct phrase and can be used in written English.
You can use "ascendancy as" to indicate someone's dominant or influential position in a certain situation. Example: "Despite his young age, John quickly gained ascendancy as the leader of the group due to his charisma and strong decision-making skills."
Funeral homes and coffin makers began their macabre ascendancy as this developing nation's foremost growth industry.
The 1929 stock market crash assured the dress's ascendancy, as overnight it became unseemly for women to flaunt their wealth.
England were now in the ascendancy, as they strove to save their reputations and their coach's job.
Even those who regard the Trump ascendancy as beyond horrifying cannot help but be mesmerised by how he's doing it.
Should Catholicism in America ever gain the same ascendancy as did French Catholicism, Tocqueville suggested, the consequences would be as disastrous.
His career is traced up from the mailroom where he worked with David Geffen, up to his ascendancy as head of IAC/InterActiveCorp.
This was a stage with a constantly evolving scenario as a lead group of a dozen fought out the lead between them, with the ascendancy changing as often as the weather, which switched every few minutes from chilly rain to warm sun as thunder rumbled around the Alps and the cloud cover moved up and down the mountain slopes.
The Tea Party ascendancy saw Romney as well as Obama shifting their positions on climate change.
If you are looking for confirmation of the genre's ascendancy to huge commercial, as well as artistic importance, then Skepta's Friday-afternoon set on the Pyramid stage seems strong evidence.
Jeremy Corbyn's ascendancy did not, as has been noted, prompt a crisis in the Labour party, rather it highlighted an existing crisis in the party.
His efforts today to turn the tables on Mr. Gore seemed to reflect not only the ascendancy of gun control as a political issue but also Mr. Bush's desire to court swing voters, many of whom favor greater regulation of firearms.
