WASHINGTON - All but five Republican senators backed former president Donald Trump on Tuesday in a key test vote ahead of his impeachment trial, signaling that the proceedings are likely to end with Trump's acquittal on the charge that he incited the Jan. 6 Capitol riot.

From the deepest conservative states to more Democratic leaning terrain, Senate Republicans face a brutal political environment that has left the GOP needing to pull off a near-perfect run in a dozen highly competitive races to retain the majority.