It took four years and an election defeat. But someone with real power inside the Republican Party is standing up to — and swatting back — President Trump: Senate Majority Leader Mitch McConnell.

Why it matters: This is a preview of the power struggle that will define the Republican Party in 2021.

You saw this with McConnell acknowledging Joe Biden as President-elect.

• You saw this with McConnell blocking Trump's push to raise stimulus checks to $2,000, which would have split Senate Republicans.
• And you're seeing it now with his effort to curtail futile resistance by the GOP to congressional certification of Biden's victory.

Yes, but: Until now, McConnell's strategy was buffeted by the chaos Trump created. Now, the Senate leader — whose autobiography is called "The Long Game" — is finally able to set the party's course.

• "McConnell is trying to reclaim the role he had in 2009 — leader of the opposition to a new Democratic president," said a Republican operative familiar with the leader's thinking.

What he's thinking: Depending on the outcome of Tuesday's Georgia runoffs, McConnell will have to find a way to protect — or regain — a Senate majority, in the face of Trump and his operatives promoting candidates who could win primaries but might well lose.

• During Trump's presidency, Axios' Margaret Talev points out, McConnell gained from an alliance that yielded 200+ lifetime judgeships — including three Supreme Court justices. As ex-president, Trump carries more liability. 

The bottom line: Beginning 19 days from now, McConnell is the most powerful Republican in the land.