'by a solid margin' is correct and can be used in written English.
You can use it in a sentence to describe a situation in which the difference between two things is significant. For example, "The incumbent candidate won the election by a solid margin."
Thanks to the left's strong majority in parliament the law passed by a solid margin.
Anti-Sarkozy sentiment gives the opposition a strong tailwind, and every poll favors Hollande by a solid margin.
The unexpected Brexit win by a solid margin (51.9% to 48.1%) has cascaded across international financial markets.
This season, the best defensive team in the league was the Indiana Pacers by a solid margin.
It worries that its leverage at the bargaining table will evaporate if Aftra members approve their contract by a solid margin.
Voters went to the polls on Sunday for a runoff between her and José Serra, the former governor of São Paulo, and chose her by a solid margin.
If accurate, these figures seem to back the preliminary count, which handed the CPP 68 seats in the 123-seat National Assembly, against 55 for the CNRP.In this section Border disorder All at sea Bad news Stand-off Drive-by shooting ReprintsThis is a solid margin, helped by blatant gerrymandering of districts.
That is a solid margin by any standard.
If accurate, these figures seem to back the preliminary count, which handed the CPP 68 seats in the 123-seat National Assembly, against 55 for the CNRP.In this section Border disorder All at sea Bad news Stand-off Drive-by shooting Reprints Related topics Sam Rainsy People's Party (Cambodia) Hun SenThis is a solid margin, helped by blatant gerrymandering of districts.
You need a solid margin on your product to cover the bounty.
The peripheral tumour showed a solid margin and there was central necrosis with cystic change.
