In other words, the entire discussion assumes at all votes have the same value or importance.
They don’t.
The canard assumes that it is possible to measure such things. It isn’t.
The canard also assumes that votes are the only things that matter. They aren’t. An elected official can hurt conservatives and advance liberal policies in many ways other than voting on the floor of Congress.
Suppose a politician had a high conservative ranking based on votes, but campaigned for liberal democrats for office. Would you call that person 80% your friend?
Indeed. I can live with the 80% rule as far as politicians who share 80% of the following views (to pick 5, so that they can falter on one of these and hold fast on the others):
Immigration/amnesty
Debt ceiling
Balanced budget
9th and 10th amendment
Closing many unconstitutional federal agencies.
Or, if a politician will fight to close 80% of the federal agencies I think should be shut, then I’ll support them.
If they will work to repeal 80% of the gun laws I think are unconstitutional, they have my vote.
If they will eliminate 80% of the unjustified power of the IRS and NSA, I’m for them.