The phrase "an influential supporter" is correct and usable in written English.
You can use it to describe someone who has a significant impact or power in supporting a cause, organization, or individual.
Example: "The campaign gained momentum thanks to an influential supporter who helped secure funding and media attention."
Alternatives: "a key advocate" or "a powerful backer."
He became an influential supporter of the Whigs (who sought to further the constitutional principles established by the Glorious Revolution) in a number of government posts.
This kind of relationship extends beyond Verizon, with labor being an influential supporter of major telecommunications companies like SBC and BellSouth with regulators.
In 1849 Gourgaud, by then a baron and a peer of France, was elected to the Legislative Assembly, where he became an influential supporter of Louis-Napoléon (later Napoleon III).
Its literary editor, JR Ackerley, who made a point of accepting or (much more often) rejecting batches of verse by return post, quickly became an influential supporter of this prolific young poet from South Shields.
Senator Edward M. Kennedy, Democrat of Massachusetts, an influential supporter of the bipartisan Senate bill, was already warning on the floor tonight that one provision of the House bill was unacceptable.
Glowering, dark-eyed Ciarán Hinds is on hand as his surly opponent, Lord Tarleton, the chief defender of the slave-trading interests, and the great Michael Gambon, with his richly musical baritone, wafts his bulk through the movie as the Whig politician Charles James Fox, who becomes an influential supporter of the abolitionists.
Dusan Lajovic certainly has a fairly influential supporter, in compatriot Novak Djokovic.
George Mason's Ilya Somin, an outspoken and influential supporter of a previous legal challenge, says the linchpin of O'Connor's thinking is "badly wrong".
After the lecture we gathered on Grassmarket and our numbers included renaissance man the photographer John Byrne, Ron O'Donnell and Thomas Reilly, a prominent and influential supporter of Glasgow Celtic soccer club.
Brad Leighton, a spokesman for the American forces, said the sheik was considered a "valuable friend" and "influential supporter" in efforts to quash the insurgency.
Indeed, it is worth noting that one of the many economists that opposed the Howe budget on the grounds that it would kill off the economy was Mervyn King, who today as the Governor of the Bank of England has been a vocal and very influential supporter of Mr. Osborne's deficit slashing strategy.
