Looks like this veto will pass in the House, as there is a clear Democratic majority to stop this Emergency Declaration, and several R Congress members joining in that veto as well. The question of course will be in the Republican Senate, and whether there is fallout from that group.
Senate Majority leader Mitch McConnell (R-KY) is following T’s requests and not challenging this, however a few R Senators will be vetoing it.
R’s Voting to Veto Emergency Declaration
Sen Susan Collins (R-ME) - facing reelection and huge backlash from her Kavanaugh vote.
Sen. Lisa Murkowski (R-Alaska)
Sen. Thom Tillis (R-N.C.)
You wonder about what Sen Manchin (D-WV) will do, as he usually votes pro-T.
The outcome was less assured in the Senate, which will be required — under provisions of the National Emergencies Act — to take up the legislation within weeks of House passage. If all Senate Democrats vote for the disapproval resolution, only four Republican votes would be needed to ensure passage, since just a simple majority vote is required.
With numerous Republican senators voicing concerns or outright opposition to Trump’s national emergency declaration, the disapproval resolution was widely expected to pass the Senate — though probably without securing the two-thirds majority that would be needed for a veto override. Senators could also potentially vote to amend the resolution, which could complicate its path to passage.
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Some of these same Republicans argued Monday that the situation is different now, because Trump is relying on a federal law that allows him to declare a national emergency and because, they said, evidence of an emergency was plentiful — even though border apprehensions are at their lowest levels in decades. Republican lawmakers have been reluctant throughout Trump’s presidency to challenge him outright, given the popularity he retains with Republican voters, and his national emergency declaration did not appear to have changed that.
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But not all Republicans were ready to support Trump. Sen. Susan Collins (R-Maine) reiterated her intention to vote for the disapproval resolution, and Sen. Lisa Murkowski (R-Alaska) suggested in an interview with an Anchorage television station over the weekend that she would probably do the same.
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On Monday, Sen. Thom Tillis (R-N.C.), who is up for reelection in a presidential battleground state, joined them, writing in an opinion piece for The Washington Post: “It is my responsibility to be a steward of the Article I branch, to preserve the separation of powers and to curb the kind of executive overreach that Congress has allowed to fester for the better part of the past century. I stood by that principle during the Obama administration, and I stand by it now.”
Senate Majority Leader Mitch McConnell (R-Ky.) had cautioned Trump beforehand about the possibility that an emergency declaration would result in a vote of disapproval that would force him to issue the first veto of his presidency. But McConnell ultimately agreed to support the declaration as Congress negotiated its way out of another potential government shutdown earlier this month.
and you-know-who 
will be none too pleased.