Sen. Mitt Romney (R-Utah) on Saturday tweeted a scathing response to President Trump's Friday night commutation of former associate Roger Stone's prison sentence, calling the move "[u]nprecedented, historic corruption."

Why it matters: Romney has emerged as the party's most prominent Trump critic. He sent shockwaves through Washington after announcing he would vote to convict Trump in the impeachment trial — becoming the only Senate Republican to break ranks and vote for the president's removal from office. Now he is the first major GOP lawmaker to condemn Trump's Friday night call regarding Stone.

Meanwhile, other Republicans have defended the president's move.

• Sen. Lindsey Graham (R-S.C.) tweeted before Stone's commutation was official: "In my view it would be justified if President @realDonaldTrump decided to commute Roger Stone's prison sentence.Mr. Stone is in his 70s and this was a non-violent, first-time offense.
• Rep. Jim Jordan (R-Ohio) wrote on Twitter that he supports the commutation, adding "Roger Stone’s prosecution by overzealous Special Counsel prosecutors was an outgrowth of the Obama-Biden misconduct."

The big picture: Stone was convicted as part of the Robert Mueller investigation for obstructing justice, tampering with witnesses and making false statements to Congress. The president's commutation cleared Stone's entire 40-month prison sentence.