In 1856, the Republicans: declared their opposition to slavery. nominated William Seward for president. stood for states' rights. strongly condemned the nativist platform of the American party. campaigned vigorously all over the country.

declared their opposition to slavery.

Explanation:

In 1856, two years after the formation of the Republican Party in 1854 Wisconsin. The Republican party presented John C. Fremont as the party's presidential candidate.

Even though the party lost to the Democratic Party who presented James Buchanan. Republicans centered their campaign on anti-slavery, by declaring their "opposition to slavery."

This made them win a majority of the Northern votes at the time.

d) a constitutional amendment

“a committee reviews the bill and marks it up to make it more viable and to reflect interests