The Note: As Robert Mueller's probe continues, increased scrutiny of his efforts

— -- The TAKE with Rick Klein

This is what political warfare looks like.

President Donald Trump is getting loads of help from his party apparatus on at least one front.

White House allies are building a case against Robert Mueller's investigation as quickly as Mueller himself does his work – or so it would appear from the limited visibility offered by the special counsel's office.

Lawyers for the presidential transition committee are sounding alarms about Mueller's work, claiming his team unlawfully accessed transition emails. The Department of Justice – which nominally, at least, oversees Mueller's work – is helping undermine faith in his team by being unusually forthcoming with information about some of his hires.

GOP-friendly media voices and leading members of Congress are laying the groundwork to question virtually any action that comes out of Mueller's operation in the coming weeks and months.

"These conflicts of interest jeopardize the integrity of his investigation," Senate Majority Whip John Cornyn, R-Texas, said on ABC's "This Week."

Insiders think Trump is very unlikely to fire Mueller – that such a move would cause an unraveling of his presidency, and that he knows it. Asked late Sunday if he was considering firing him, the president responded, "No, I'm not - no."

Neutering Mueller in the court of public opinion may be the last best option available to the president's defenders.

The RUNDOWN with MaryAlice Parks

All signs suggest that America will have a new tax code signed into law by the end of the week. The votes may be tight, and, as is often the case with big pieces of legislation, the final tally will probably come to the wire. Still, Republicans seem confident they will pass their plan before Christmas as promised and suggest they even have least once vote to spare.

Sunday night, Sen. John McCain's office confirmed that the Arizona senator, who is battling brain cancer, was headed home even though it mean he would miss the roll call.

The GOP will likely get momentary political boost for (finally) sending a major bill to the president's desk, but in the end voters will judge the plan on how it affect them and whether or not they see any benefit to their families, job prospects or wallets.

Republicans promised simplification, but the final bill is over 1000 pages. Many of the deductions that were scrapped initially managed to squeeze their way back in as the bill got shopped around Washington and debated in the public eye.

And yes, the wealthiest few and biggest corporations still stand to gain the most.

The TIP with Meridith McGraw

Senator Bob Corker, R-Tenn., wants to know why a last minute provision that provides a tax break to people with significant commercial real estate holdings was added to the Republican tax bill.

"Because this issue has raised concerns, I would ask that that you provide an explanation of the evolution of this provision and how it made it into the final conference report," wrote Corker in a letter to Senate Finance Chairman Orrin Hatch.

The International Business Times reported the provision could benefit Corker, who has sizable commercial real estate holdings, and is a crucial "yes" vote for the Republican tax bill. Corker denies requesting any special tax provisions in order to win his vote.

The tax break has raised the eyebrows of Senate Democrats like Sen. Chris Van Hollen, D-Md.

"I don't know how it got in," Van Hollen told George Stephanopoulos on "This Week." "What we do know is they're behind closed doors. There are a whole army of lobbyists who were surround them, and the longer they're in there, the more you see these special interest provisions, George."

WHAT YOU NEED TO KNOW TODAY:

QUOTE OF THE DAY

"So millions of American taxpayers handing over money to foreign stock holders. It doesn't sound like America first to me. It doesn't sound like middle class first." - Sen. Chris Van Hollen, D-Md, on the tax form bill that will allow foreign stock holders a $31 billion tax break in 2019.

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The Note is a daily ABC News feature that highlights the key political moments of the day ahead. Please check back tomorrow for the latest.