“I think it was the Whig party that became the Republican party.”
No. The Republican party is not an extension of the Whig party.
The Republican party was formed by a coalition of Democrats and Whigs. And, despite what other may say, the primary driver was opposition to slavery.
The Democrats were pro-slavery. The Whigs a “we don’t like it, but there’s nothing we can do about it, so we’re not going to try” attitude.
The Republican Party was formed to “abolish slavery and restrict the role of government in economic and social life.” That quoted line was the agreed upon purpose of the founders of the Republican party.
The Republican party was a 3rd party. Eventually the Whig party disappeared, because people left it for either the Democrat or Republican party.
Somehow I kind of remember that the Republican party was formed out of some of the Whig people. But then, my adage is: “You’ll always meet someone smarter than you and learn from it”
I don't think the republicans were ever a third party, when they formed in 1854, the Whigs were only 22 years old.
The republicans simply replaced the Whigs, two years after they first met in 1854, John Fremont came in second in the 1856 presidential race, the “know Nothings” “third party” came in a distant third with 8 electoral votes. The Whigs were pre civil war America, the party only lasted 22 years itself (1833 to 1856). The Republicans held their first convention on July 6, 1854 and four months later held 19% of the Congress and 25% of the Senate, six years later they held the majority in the Congress, the majority in the Senate, and they had the Presidency. The Republicans were never really a third party at all.