You can't impeach a US senator. They are difficult critters to get rid of.
Were Romney not part of the LDS elite, he would not be a senator from Utah, but the deal is done and they will make certain he is in the senate until he goes to Kolob. He's like Tom Harkin was in IA, Ted Kennedy in MA and the late McNoName in AZ: senator for life or until he can't go any further.
I wish Romney’s Lord would give him a one-way express ticket to Kolob soon!