Hughes is a research specialist at the University of Virginia.
Once, not so long ago, congressional Republicans were impeachment's constitutional stalwarts.
They stood up for the House's "sole power of impeachment," a power granted in the Constitution, including the right to subpoena witnesses and evidence. Even when the president under investigation was a Republican. Even when the Republican political base threatened to turn against them.
But that was when the president was Richard Nixon, not Donald Trump.
With the Senate trial about to get started, a look back is in order.
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