The phrase "a demonstration of support for" is correct and usable in written English.
You can use it when describing an action or event that shows backing or endorsement for a person, cause, or idea.
Example: "The rally was a demonstration of support for the new environmental policies proposed by the government."
Alternatives: "an expression of support for" or "a show of support for".
And then they show this on television as a demonstration of support for Putin".
"What you see here today is a demonstration of support for our leader, Moqtada al-Sadr," he said.
Initiated by dozens of local groups across the country, this mass action was a demonstration of support for the women of Greenham.
Some members of the Obama team were convinced of the need for humanitarian intervention and a demonstration of support for the Arab spring.
Mrs. Bush's visit was a demonstration of support for Mr. Karzai and his government as it prepared to ask for about $50 billion in pledges of assistance from international donors at the conference this week.
Mr. Barak's remarks were made in an address the Israeli Parliament at its first plenary session outside Jerusalem, a demonstration of support for communities on the northern frontier following Israel's troop withdrawal from southern Lebanon.
An event unlike any of its kind, it's the one time of year (save for the Bushwig Drag Festival) that this massive, performance-focused community simultaneously comes together in a demonstration of support and celebration for their fellow queers.
Speaking in hushed tones, several people said any demonstration of support for the mayor like displaying a sign demanding his release would bring immediate arrest.
Sae-A's demonstration of support for Haiti is illustrated through its donation of clothing, equipment and medical supplies as part of relief efforts, building a school for 450 students, and supporting a medical services mission.
One of them told me they had all paid their own air fares, a public demonstration of support for their president.
As the Dutch prime minister, Jan Peter Balkenende, appealed for calm, more than 10,000 people poured into Amsterdam's central square in an emotional demonstration of support for Van Gogh and against violence.
