The Republican battle lines being formed in President Trump's final days — his loyalists vs. Senate Majority Leader Mitch McConnell's establishment — will shape American politics for the next four years. 

Why it matters: This power struggle will help define everything from the future of conservatism and right-wing media to President-elect Biden’s ability to win Republican cooperation in office. More broadly and more importantly, the outcome will determine if Trumpism — and its norm-smashing tactics — come to permanently define one of America's two major political parties.

The camps are clear as we begin this epic political month:

• The Trump camp includes House Republican Leader Kevin McCarthy, the 12 senators and 140+ House members who plan a futile fight Wednesday against certification of Biden’s victory. That group includes GOP 2024 hopefuls, including Sen. Josh Hawley of Missouri and Sen. Ted Cruz of Texas.
• With Trump out of office, McConnell will be the GOP’s de facto leader, backed by Sen. Mitt Romney of Utah and other establishment types who don't have to worry about primary challenges from the right, where Trump has shown he’s willing to play a decisive role.

Look for McCarthy to straddle the camps.

• So will Sen. Tom Cotton of Arkansas, primed for a 2024 presidential run. Cotton, a vocal Trump ally, announced last night that he won't join the protest: "[O]bjecting to certified electoral votes won’t give him a second term."

Between the lines: Some top Republicans tell us this split will blur. McConnell is unlikely to chart a true separation, and will do plenty for Trumpy Republicans in coming years.

• McConnell has greater street cred with the base than he did a few years ago, after helping Trump seat three justices on the Supreme Court.

🥊 Former House Speaker Paul Ryan, the Republican vice-presidential nominee in 2012, who has said little since leaving office, issued a scathing statement about the lawmakers' planned resistance: