Stephen Miller, President-elect Trump's deputy chief of staff, is asserting himself as the key player in the White House's plan to pass Trump's sweeping agenda through Congress.   Why it matters: Trump trusts Miller implicitly, as does incoming Chief of Staff Susie Wiles, with whom Miller worked hand-in-glove on the campaign.

• Miller has become instrumental as Senate GOP leader John Thune (R-S.D.) and House Speaker Mike Johnson (R-La.) haggle over how to pass MAGA priorities, fast.
• Miller also gets Congress: While he initially called for a two-bill approach to immigration and tax reform, he has not publicly voiced his preference since Trump indicated he wants one "big beautiful bill."
• But Miller's allies inside Trumpland, not to mention senators and lawmakers, know that his top priority is immigration.

Zoom in: In a sign of the kind of power he wields, Miller presented alongside Trump during Wednesday's meeting with senators.

• Miller used the opportunity to provide a detailed plan of attack for Trump's first 100 executive orders, as Axios scooped.
• "Senators know that he's not just speaking faithfully to what the Trump Team wants, but he's offering counsel on how to enact the policies that we care about," said Arkansas Sen. Tom Cotton.

Also in the meeting were Wiles, incoming deputy chief of staff James Blair and James Braid, Trump's incoming director of the Office of Legislative Affairs.

• While Miller talks policy, Braid — who previously served as Vice President-elect Vance's deputy staff chief in the Senate — and Blair will be taking over the process of getting the legislation passed.

Between the lines: Miller is one of the few Trump II officials who served in Trump I, and he served all four years, which was a rarity.

• He has frontline experience in the Senate, where he served as a top adviser to former Sen. Jeff Sessions.
• "It seems very clear that if you want to get a piece of legislation done, you got to work with Stephen Miller," a top adviser to a GOP senator told Axios.

What we're hearing:  Miller's allies — and even his enemies on the left — say that he derives much of his power from his deep understanding of immigration and the border.

• "No one knows more than Stephen on this," one Trump adviser told Axios.
• "Stephen is the Swiss Army knife for Trump: He does the policy, the politics and the media," a Trump insider told Axios.
• Miller is previewing his tactical plans to stem illegal immigration: "We are going to use the Defense Department to secure the border of our country," he told Newsmax.
• Miller did not respond to a request for comment.

Insiders say Miller, 39, has improved his bedside manner from Trump's first term, when he rubbed some staffers and Hill leaders the wrong way.

• "In the past, he would just bull rush to get his way and he didn't care what enemies he made," said a third Trump adviser.
• "Now he works the sh--t out of everybody. ... Yeah, he has the ear of the president, but now he gets allies so that he can just have surround sound."

The intrigue: Senators frequently discuss what they have heard from Miller on reconciliation strategy — more than any other Trump team member, a senior Hill aide told Axios.

• Miller is also discussing Trump's tax and foreign policy with lawmakers.

Zoom out: With inauguration 10 days away, House and Senate Republicans are locked in a staring contest over a tactical question that has consumed Congress: one or two bills.

• Trump seems content to let them fight it out. The House and Senate are basically pursuing two parallel tracks, racing for a finish line neither side can define.

The bottom line: Miller is seen by many as not just Trump's man on the Hill, but one of the most influential figures in Washington.

• "Stephen right now looks like he'll be the most powerful unelected man in the White House," said another Trump adviser, who added that "Susie Wiles is the most powerful Trump appointee, and Stephen knows that and she's happy to let him do his thing."

President-elect Trump is preparing to invite the entire Senate Republican conference to Mar-a-Lago for a mega-MAGA party in the coming weeks, people familiar with the matter tell Axios.

Why it matters: Trump is keen to celebrate a victory he sees as historic and fete the senators who helped him achieve it. He also wants to build trust with the lawmakers he needs to pass his sweeping legislative agenda.

• "Mar-a-Lago is special to the president. He's at ease there. Everyone is," a Trump adviser told Axios.
• "So it's a good place to get everyone together outside of Washington. It's team bonding. Trump is very much the player-coach."

Driving the news: Final details have not been locked down, but the big bash could come before Trump's inauguration.

• It will serve as an informal and more fun follow-up to his meeting Wednesday evening with GOP senators at their weekly policy get-together.
• Trump is also hosting governors at Mar-a-Lago on Thursday night, Politico reported.
• Also this week, Trump will welcome three House groups to his Florida club. There'll be separate meetings scheduled for the Freedom Caucus, committee chairs and the so-called SALT lawmakers from high-tax blue states.

Zoom out: Trump likes to play the role of DJ at his Palm Beach club, but the background music will likely be dominated by the same talk that has consumed D.C. these last few weeks.

• Republicans are in a heated internal conversation on whether to use one — or two — legislative vehicles to implement Trump's immigration and tax reform policies.

Trump isn't entirely indifferent, but he's indicated he can live with either approach.

• "I like one, big, beautiful bill," Trump said at a press conference on Tuesday. "But if two is more certain, it does go a little bit quicker because you can do the immigration stuff early."
• "I can live either way," he added.

Zoom in: This winter, Mar-a-Lago has been the warm-weather retreat for Trump's court — once in exile, but now preparing to return to power. (Mar-a-Lago was dubbed the "Winter White House" long before Trump bought it).

• Government leaders and high-profile executives have all visited Trump in Palm Beach, both to pay their respects, but also to understand Trump's intentions and shape his views.