The phrase "an enthusiastic backer of" is correct and usable in written English.
You can use it to describe someone who strongly supports or advocates for a particular cause, project, or individual.
Example: "She is an enthusiastic backer of renewable energy initiatives, believing they are crucial for a sustainable future."
Alternatives: "a passionate supporter of" or "a fervent advocate for".
Manhattanville's president, Richard Berman, has been an enthusiastic backer of the Valiants' rise.
He is an enthusiastic backer of Trump's promise to build a wall on the border with Mexico.
The Christian Democratic Union, the most sceptical big party, was an enthusiastic backer of the Tempelhof referendum, notes Volker Mittendorf of the University of Wuppertal.
He became an active Fascist, an enthusiastic backer of Mussolini, and argued in Futurismo e Fascismo (1924), that Fascism was the natural extension of Futurism.
Russell Ivanovic, of the Australian app company Shifty Jelly, is an enthusiastic backer of Android Wear, which he says is "a far superior platform to the Apple Watch.
Truss has been an enthusiastic backer of British farmers and food but has been much less vocal on the natural environment.
Mr. Schwarzenegger was an enthusiastic backer, insisting the problem of runaway production had too long been ignored by Hollywood and Sacramento.
It was an early, enthusiastic backer of charter schools.
But he was also an often enthusiastic backer of federal support for basic research, especially research into renewable energy technologies.
Naturally wanting to be funky and web 2.0 all the candidates have MySpace pages - although Barack Obama had a bit of a spat over a profile run by an enthusiastic backer - that MySpace have rounded up as part of a recently launched community area called the Impact channel.
When the two men differed over charter schools (Cuomo is an enthusiastic backer, de Blasio is more skeptical), the Governor supported a multi-million-dollar television campaign against the Mayor's position.
