The phrase 'supported him in' is correct and usable in written English.
You can use it to indicate that someone gave assistance to another in some way. Example: She supported him in his efforts to find a new job.
I supported him in the past.
I supported him in 2000, and I support him now".
His wife, Peggy, supported him in his quest.
That must have been obvious too to those politicians who supported him in Parliament.
Moreover, despite their ideological differences, Mr Klaus has supported him in the past.
But having supported him in the past, many voters seem to be moving away.
This newspaper supported him in 2008 and backed his disappointing-but-necessary health-care plan.
Other important leaders who supported him in that period were Zhou Enlai and Zhu De.
His many followers supported him in a manner befitting the nobility.
Miners and mine owners have supported him in his Senate races.
Rochester's two daily newspapers supported him in 1984 but have endorsed Slaughter this year.
