When did the conservative/liberal alignment take place?

[Statilius the Epicurean]

Liberals took over the Democratic Party in 1896 with the absorption of the Populist Party and conservatives permanently gained the upper hand in the Republican Party when Taft beat Roosevelt to the nomination in 1912. But each party becoming ideologically uniform was a long, long, long process which slowly happened over the entire next century: at the federal level Lincoln Chafee was probably the last liberal Republican and only lost in 2006, and Dan Lipinski is a conservative Democrat in the House and survived a primary challenge last year.

[Statilius the Epicurean]

Grover Cleveland was probably to the right of Benjamin Harrison in 1892. Harrison was moderately pro-silver, passed anti-trust legislation and tried to advance civil rights.

I'm sure there's an alternate universe where free silver Populists are absorbed into the Republican Party instead of the Democrats as historically and the GOP becomes the progressive party of popular economic reform.