The phrase "a potent ally" is correct and usable in written English.
It can be used to describe someone or something that is a strong and effective supporter or partner in a particular context.
Example: "In the fight against climate change, renewable energy sources are a potent ally for environmental activists."
Alternatives: "a powerful supporter" or "a strong partner."
Now Dr. Strayer's research has gained a potent ally.
Fascinated by their presence, Goddard wondered, "Am I their social-media darling?" Anonymous was a potent ally.
But as a new administration prepares to enter the White House, the crisis could end up being a potent ally for change.
Its civil society, according to anecdotal evidence from journalists and academics, contains much sympathy for the US; it may prove a potent ally in turning Iran away from support for terrorism and studied nuclear ambiguities.
The Kurds, who are among the most pro-American people in the world, would welcome the coalition presence and their army - by far the best indigenous Iraqi military force - would be a potent ally if it were necessary to attack al-Qaida in the Sunni Arab region.
Beyond Europe – in America in particular – we are seen as more of a force for good, and a more potent ally, inside the EU than outside.
But Clegg's view was supported by Peter Westmacott, Britain's ambassador to Washington until January, who writes in the Guardian that, "in America we are seen as more of a force for good, and a more potent ally, inside the EU than outside".
Such concerns stem in part from the fact that the arrangements could deprive prison reformers of an unlikely but potent ally: the prison guard union.
The industry's politically potent ally, the National Rifle Association, which represents 3.8 million gun owners, plans to spend a record $15 million on state and federal elections this fall.
By the time the day was over, he had become her most potent ally in the battle against TB 117.
"The preachers still feel the need of the press as their most potent ally in their work," said The Methodist Review in 1889.
