The House appears poised to override President Trump’s veto of the must-pass annual defense policy bill, a dramatic rebuke of Trump in the final days of his presidency.

House lawmakers will vote Monday on overriding Trump’s rejection of the fiscal 2021 National Defense Authorization Act (NDAA), which passed both chambers of Congress with more than the two-thirds majority needed to overcome a veto.

Some Republicans have said they would sustain Trump’s veto despite supporting the bill earlier this month. Still, dozens would need to flip their vote for the override to fail, and some Democrats who previously voted against the measure could switch their votes to override Trump.

Top House Democrats are projecting confidence they have the votes needed to deliver the first veto override since Trump took office.

“The FY21 NDAA passed with overwhelming, veto-proof support in both the House and Senate, and I remain confident that Congress will override this harmful veto,” House Armed Services Committee Chairman Adam Smith (D-Wash.) said in a statement after Trump vetoed the measure on Wednesday. “While the president may not care about our service members and their families, Congress still places an immense value on their service and sacrifice.”

Speaker Nancy Pelosi (D-Calif.), calling Trump’s veto “an act of staggering recklessness,” said in her own statement the chamber will “take up the veto override with bipartisan support.”

Including this year’s defense bill, Trump has issued nine vetoes during his presidency.

Republicans have been largely reluctant to vote against Trump over the past four years. But Trump may have met his match in the NDAA, a bill he has never before vetoed.

Lawmakers are immensely proud of the bill’s 59-year streak of becoming law and do not want to be remembered as the Congress that failed to deliver. The $740 billion legislation authorizes funding for jobs, military bases and weapons manufacturers that affect nearly every congressional district and state. Troops would lose out on a host of special pay and bonuses without passage of the NDAA.

Lawmakers on both sides of the aisle have also been stressing the importance of cybersecurity provisions in this year’s bill after a massive hack suspected to have been carried out by the Russians compromised myriad government systems at key agencies.

“We’ve just had one of the worst cyberattacks against us in our history. We experience threats from around the world every day. Our troops deserve a pay raise and it is our duty to keep America safe,” tweeted Rep. Will Hurd (R-Texas), who is retiring at the end of this Congress. “Our goal was to rebuild our military and defend our nation. The NDAA does just that and it modernizes our forces. I will be supporting it again.”

Trump’s veto of the defense bill is just one of the ways he has thrown a wrench into the final days of this congressional session.

The president late Sunday signed a $2.3 trillion government funding and coronavirus relief package, but only after offering surprise objections a day after the measure negotiated by his administration was passed by the House and Senate. 

He signed the bill a day after unemployment benefits extended by the measure ran out, but before a government shutdown would have been triggered on Tuesday.

Lawmakers in both parties had called for him to sign the measure, and Trump ultimately relented even while continuing to criticize it.

On the NDAA, Trump has offered several shifting explanations for his opposition. He first threatened to veto it over a requirement that Confederate-named military bases be renamed.

He then demanded lawmakers add a provision that would repeal an unrelated tech liability shield law from 1996 that he has been fixated on as Twitter appends corrective labels to his posts making unsubstantiated allegations of widespread voter fraud in the 2020 presidential election.

Trump has also complained the defense bill is weak on China, despite several provisions aimed directly at Beijing, such as the creation of a $2.2 billion fund specifically to counter China.

And he has lashed out at provisions designed to put up roadblocks over his orders to withdraw thousands of U.S. troops from Afghanistan and Germany.

“My administration has taken strong actions to help keep our nation safe and support our service members. I will not approve this bill, which would put the interests of the Washington, D.C., establishment over those of the American people,” Trump said last week in his veto message to Congress that also called the NDAA a “gift” to China and Russia.

Lawmakers in both parties had urged Trump publicly and privately not to veto the NDAA. They were also hoping a strong enough bipartisan vote would dissuade Trump from vetoing the bill, which passed the House in a 335-78 vote, followed by an 84-13 vote in the Senate.

After Trump’s veto, Republicans were largely quiet.

House Minority Leader Kevin McCarthy (R-Calif.) has previously said he would not override Trump’s veto despite voting in favor of the bill. His No. 2, House Minority Whip Steve Scalise (R-La.), voted against both the compromise bill this month and the initial House version in July.

But the No. 3 House Republican, Rep. Liz Cheney (Wyo.), is urging her colleagues to override Trump.

“Without timely passage of the FY2021 NDAA, thousands of military families will be forced to lose their hazardous duty pay during the holidays. Given the sacrifices they and their families make for the cause of freedom, our troops should never have their livelihoods threatened by political battles in Washington, D.C. In addition to hurting our troops, failing to pass the NDAA will have dire consequences for our national security,” Cheney said in a statement after Trump’s veto.

“Congress must uphold its highest responsibility — providing for the defense of this nation — and ensure this bill becomes law,” she added.

One wild card is the possibility that some House lawmakers might not return to Washington for Monday’s vote, for various reasons. Some might not want to travel during the height of the pandemic or already have the coronavirus, while others might not feel compelled to come back for a single day because they are retiring or lost reelection.

Many Democrats have voted by proxy during the pandemic, but Republicans have largely opposed the practice. Overriding a veto requires two-thirds of those voting, not two-thirds of the entire chamber.

Rep. Rick Larsen (D-Wash.) said the possibility of absences coupled with the GOP’s refusal to vote by proxy would help the House easily override Trump’s veto.

"That's all to our advantage,” Larsen, who recently tested positive for COVID-19, said last week.

The unusual post-Christmas session is necessary to meet a deadline to override the veto by noon on Jan. 3, when the 117th Congress starts. If lawmakers fail to override the veto before then, the new Congress would need to start from scratch on the bill.

A Democratic House aide previously told The Hill the lower chamber needs to send the veto message to the Senate by Tuesday to overcome any procedural hurdles in the upper chamber and finish by Jan. 3.

If the House fails to muster two-thirds support on Monday, the override effort dies.

But if the House successfully overrides Trump as expected, action then moves to the Senate, where any one senator who supports Trump’s veto could drag out procedural hurdles by forcing a separate vote.

The Senate is planning to convene Tuesday to start the process if the House is successful on Monday.

Sen. Rand Paul (R-Ky.), who briefly held up passage of the NDAA earlier this month, has indicated he could similarly delay an override vote.

“I very much am opposed to the Afghan war, and I’ve told them I’ll come back to try to prevent them from easily overriding the president’s veto,” Paul told reporters last week. 

Senators have suggested the final override vote could happen the morning of Jan. 3, just hours before the new Congress is sworn in. Sen. John Thune (S.D.), the No. 2 Senate Republican, warned last week it could take a "few days" for the Senate to jump through all the procedural hoops.

Senate Armed Services Committee Chairman James Inhofe (R-Okla.), who has been loyal to Trump on everything but this year’s NDAA, urged Congress to override the veto, saying troops “shouldn’t be denied what they need — ever.”

“The NDAA has become law every year for 59 years straight because it’s absolutely vital to our national security and our troops. This year must not be an exception,” Inhofe said in a statement after Trump’s veto. “I hope all of my colleagues in Congress will join me in making sure our troops have the resources and equipment they need to defend this nation.”