WASHINGTON (AP) — Republican opposition to impeaching President Donald Trump began crumbling at the party's upper echelons on Tuesday as the No. 3 House GOP leader said she would vote to impeach Trump.

"There has never been a greater betrayal by a President of the United States of his office and his oath to the Constitution," Rep. Liz Cheney, R-Wyo., said in a statement that, while not unexpected, shook Congress as lawmakers prepared for a Wednesday House vote. With Democrats commanding that chamber, a vote impeaching Trump for an unprecedented second time seemed certain.

More ominously for a...