when did he become the latter one?
1855.
Charles S. Morehead
. Accordingly, when the Know Nothing candidate for governor, Judge William Loving, withdrew from the race due to failing health, the influx of ex-Whigs nominated Morehead to replace him for the gubernatorial election of 1855. Prior to the dissolution of the party, most had expected the Whigs would nominate Morehead at their own party's convention in April.

Though Kentucky had only a small population of immigrants and Catholics, much of Morehead's campaign oratory was directed against these groups. Most of the state's immigrant and Catholic population resided in Louisville, and tensions there reached a climax with an anti-foreign riot known as "Bloody Monday" on August 6, 1855. Morehead won the election with 69,816 votes to 65,413 votes for Democrat Beverly L. Clarke. In his inaugural address, Morehead denounced the nullification of the Fugitive Slave Act and despite his campaign rhetoric, proclaimed "perfect equality" for naturalized citizens.

what was charles s. morehead's profession? Politician. which political roles did he play? U.S. Representative from Kentucky and Governor of Kentucky.
wiki:11089944
Charles S. Morehead [SEP] Governor of Kentucky
Following his congressional tenure, Morehead resumed his law practice and management of his plantations. In 1852, he was a presidential elector for Winfield Scott, and in 1853, he served another term in the Kentucky House. By early 1855, sectional divisions had ripped apart the national Whig Party. In Kentucky, many former Whigs associated with the Know Nothing Party. Morehead was among these; he claimed that the Know Nothing Party was more "Union" than the Democratic Party. The ex-Whigs hoped to take over the Know Nothing Party and reshape it into a Unionist Whig organization. Accordingly, when the Know Nothing candidate for governor, Judge William Loving, withdrew from the race due to failing health, the influx of ex-Whigs nominated Morehead to replace him for the gubernatorial election of 1855.