The provision of the Constitution giving the war-making power to Congress, was dictated, as I understand it, by the following reasons. Kings had always been involving and impoverishing their people in wars, pretending generally, if not always, that the good of the people was the object. This, our Convention understood to be the most oppressive of all Kingly oppressions; and they resolved to so frame the Constitution that no one man should hold the power of bringing this oppression upon us. But your view destroys the whole matter, and places our President where kings have always stood.
Lincoln was against the Mexican-American War because he believed the President lied about the provocations, in order to get the US into war. That the President ramrodded Congress into an expensive war with no real end point. Lincoln voted for a resolution stating the President had violated the Constitution.
In a speech to Congress, he laid out all the lies he felt Polk had used to drive the US into war. He did this in spite of strong political pressure from his own party.
Or as the Who told us: