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[ notice that Thune is at the bottom; cassidy & mcconnel WAY below Graham]

Most Conservative (Top Tier)These senators consistently score near or at 100% on Heritage Action, CPAC, and similar indices. They are frequently highlighted for strong records on limited government, social conservatism, and opposition to spending/regulation.

Mike Lee (UT) — Frequently #1 or top 3; 100% Heritage.
Ted Budd (NC), Jim Banks (IN), Bernie Moreno (OH) — 100% Heritage; strong newcomers/alignments.
Marsha Blackburn (TN), Ted Cruz (TX), Rick Scott (FL) — Top GovTrack ideology; high 90s-100%.
Rand Paul (KY), Josh Hawley (MO), Tommy Tuberville (AL), Roger Marshall (KS), Cynthia Lummis (WY) — Top CPAC; libertarian-leaning or populist conservatives.

Others in this group: Steve Daines (MT), Kevin Cramer (ND), Mike Crapo (ID), Bill Hagerty (TN), John Cornyn (TX) (high 90s Heritage), Tom Cotton (AR).Strongly Conservative (Solid Majority of GOP Senators)Most Republican senators score in the high 80s–mid-90s. Examples (from available data):

John Barrasso (WY) (~94% Heritage)
Chuck Grassley (IA), Joni Ernst (IA) (~94%)
John Curtis (UT) (~94%)
Bill Cassidy (LA) (high 90s in some metrics)
Marco Rubio (FL), Tim Scott (SC), Katie Britt (AL) (generally strong, though Britt slightly lower in one scorecard at ~78%)
Lindsey Graham (SC) (~76%, but higher on national security)
Many others like Thom Tillis (NC), Shelley Moore Capito (WV) fall here or slightly lower depending on the year.

More Moderate/Least Conservative RepublicansThese have lower scores due to occasional bipartisan votes, institutionalism, or state-specific moderation (e.g., blue/purple states):

Susan Collins (ME) — Often the lowest (e.g., ~18% in one Heritage snapshot; consistently moderate across indices).
Lisa Murkowski (AK) — Frequently among the lowest GOP scores (e.g., mid-50s or lower on CPAC).
Mitch McConnell (KY) (retired or reduced role) — Lower scores in recent years (e.g., 68% CPAC).
Deb Fischer (NE) (~76% Heritage), John Boozman (AR) (~76%), Shelley Moore Capito (WV) (~76%).
Others occasionally noted as relatively moderate: Bill Cassidy (LA) on some votes, John Thune (SD) (leadership role leads to more compromise).