The phrase "a substantial margin and" is correct and usable in written English.
It can be used when discussing differences, advantages, or excesses in various contexts, such as finance, competition, or performance.
Example: "The company reported profits that exceeded expectations by a substantial margin and demonstrated strong growth potential."
Alternatives: "a significant margin" or "a considerable margin".
I reckon a quick straw poll of Sweden's neighbours would see it voted the world's självgodaste country by a substantial margin, and I'd vote for that, too.
"The actual physical asset underperforms equities by a substantial margin, and there are going to be long sustained periods when it underperforms significantly.
Banda was defeated by Bakili Muluzi of the UDF by a substantial margin, and the UDF won a majority of seats in the National Assembly.
The bold maneuver would probably be used only if the team were trailing by a substantial margin and in desperate need of a spark.
A poll conducted online for Channel Four television showed the Conservatives leading his Labor Party by a substantial margin, and another online poll, for The Times of London, showed that confidence in Mr. Brown's competence as prime minister had fallen.
Paramilitary and police forces outnumber the active-duty military by a substantial margin, and years of civil unrest have forced the government to rely on such forces divided among several ministries and directorates both for internal security and, often, for quelling internal dissent.
Pro-Canada forces won by a substantial margin in 1980 and by only a whisker - roughly 50,000 votes - in 1995.
Yahoo! is No. 1 by a substantial margin in Japan and Korea, and statistics now coming out of Europe show it is working its magic there as well.
Hillary Clinton won the popular vote by a substantial margin — more than two and a half million votes — but, under the baleful metrics of our Electoral College, the outcome was not especially close.
It outperformed the second best program by a substantial margin on many measures and by a small but significant margin on others.
"We're going to have a six- or seven-point victory and a substantial margin in the Electoral College of 320 votes or so," Mr. Rove said.
