The Democratic-led House has already approved a resolution to block Donald Trump’s emergency declaration, in which the president granted himself the authority to redirect funds to border barriers in defiance of Congress’ wishes. Next week, the Senate will take up the same measure, and a bipartisan majority is already in place to pass it, which will force Trump to issue the first veto of his presidency.

In fact, opponents of the White House’s plan only needed four Republican senators to break ranks – and those four votes are already in place. One member of the quartet, Sen. Susan Collins (R-Maine), said this morning that the total number of GOP votes against Trump’s gambit may very well grow.

It’s an outcome the White House clearly hopes to avoid. It’s why the president tweeted on the subject yesterday …

“Senate Republicans are not voting on constitutionality or precedent, they are voting on desperately needed Border Security & the Wall. Our Country is being invaded with Drugs, Human Traffickers, & Criminals of all shapes and sizes. That’s what this vote is all about. STAY UNITED!”

… why Vice President Mike Pence is lobbying lawmakers on the issue …

Vice President Mike Pence and other Trump administration officials are calling on senators to back President Donald Trump’s emergency declaration to build his southern border wall, citing an increase in illegal border crossings in recent months. Vice President Mike Pence on Wednesday criticized lawmakers from both parties who plan to support a resolution to block the president’s emergency declaration.

.. and why White House Press Secretary Sarah Huckabee Sanders is blaming Congress for not simply meeting Trump’s demands in the first place.

“My message to that group is to do your job,” she said during an appearance on Fox News’s “Fox & Friends.” “If you had done what you were elected to do on the front end, the president wouldn’t have to fix this problem on his own through a national emergency.”

The broader question, however, is why Team Trump is suddenly making such a hard sell.

Looking ahead, we already know where this fight is likely to end up. The House passed its resolution, the Senate will soon do the same, and the president will veto the measure. At that point, the bill will return to Capitol Hill, where there is very little chance lawmakers will be able to override the veto and kill Trump’s policy.

So why would the White House, confident of the ultimate outcome, feel the need to fight?

Part of this dynamic is purely political. Trump assumed – and publicly predicted – that Republican lawmakers would follow his lead, and when Congress passes this resolution with bipartisan support, it will be deeply embarrassing. Polls already show the public opposing the president’s gambit, and this will only make matters worse.

Trump places a high price on partisan loyalty. Watching his ostensible GOP allies try to block his top domestic priority serves as a reminder of his failure to keep Republicans together and to make a persuasive case.

But I continue to think the legal considerations are just as important, if not more so. Once the veto-override efforts fail, it’ll be up to the courts to consider challenges to the president’s policy, and it’s very likely that judges will take note of the fact that bipartisan majorities in the Democratic-led House and Republican-led Senate both approved a resolution rejecting the president’s scheme.

At least for now, however, there doesn’t appear to be much the White House can do about it.