I am sorry, I did not make it clear, the quote. I was quoting verbatim from the Book "The Civil War: An illustrated History by Geoffrey Ward with Ric Burns and Ken Burns. Chapter 1: 1861 House Divided, under the Section/heading the Momentous Question page 17 third paragraph, I abbreviated it. The Passage in the book did not specify the date, recorded in the senate records. Abraham Lincoln was certainly a politician. He makes this quote, but a short time later, he is running for the Presidency on the new Republican platform. In looking at the platform of the Republican Party and stance, they were wanting to develop the western lands, for all free white men. They wanted to stop slavery in the west, and prevent it from coming North. The North's big fear was that the Southern States might bring slavery North, and change the States power structure, and they would vote with the southern slaveholding states. The political struggle on the North side was the very similar, it was political control of the Union by their region, the North felt that South would have undue power and influence in the House and Senate, and that they would really hamper Northern Industry. The South viewed that they would have no power or voice in Congress unless slavery was extended. They had a great fear of the Abolitionists seizing control of Congress and outlawing slavery completely in the South and all US territories, without the population density of the North, without the working capital and wealth of the North, with out all the industry and material and goods, the South was faced with having nothing.
Again quoting from Ward and Burns Page 24 last paragraph continuing to page 25:
"Many SOUTHERNERS OPPOSED slavery and thought talk of Secession Madness. There were whole regions of the South where Cotton was NOT King, where poor upcountry farmers, who owned NO slaves, had nothing but contempt for the prosperous lowland planters who did. "All they want is to get you to fight for their infernal negroes," said a farmer from Winston County, Alabama, "and after you do their fightin, you may kiss their Hin' parts for all they Care."
"Some in the North hated slavery because it was wrong; others opposed it because they thought it threatened the job of wage earners; still others condoned it because there was money to made. "the business of the North as the well as the South has become adjusted to it," wrote a New York Merchant. "There are millions upon millions of dollars due from Southerners to the merchants and mechanics of this city alone, the payment which would be jeopardized by any rupture between the North and the South. We cannot afford to let the abolitionists to succeed in their endeavor to overthrow slavery. It is not a matter of principle with us. It is a matter of Business Necessity."

Page 26 (Ward and Burns) Chapter 1: 1861 House divided, The Momentous Question
"Persuaded that the Constitution forbade presidential action against slavery where it already existed, Lincoln was nonetheless pledged to halt its further spread. "On that point," he told his supporters, "hold firm, as a chain of steel. the tug has come and better now than anytime hereafter."

My Commentary:
Proof positive, Politics in the North was a major factor. Lincoln flipflopped like a bass on the boat deck with the issue of slavery. to appease both sides of Northern politics, and with his strict interpretation on the Constitution, Lincoln deliberately stated in the Emancipation Proclamation that the slaves would be freed only in the States in Rebellion and had been subdued by the Army, and upon reentry, then it would be like a new state coming into the Union and Slavery. Legally by reentering the Union would be abolished in that state, and was legal to do so, according to Lincoln's interpretation of the Constitution and the laws passed by Congress.

The Constitution and Congressional Legislation, did not cover States in Rebellion. In Lincoln's mind, the South did him a favor. The slavery issue died the day of the Emancipation Proclamation was signed, and rendered it a mute point for the North. North and South realized that no matter what, slavery would not be tolerated as a result of the War. By this stroke of the pen, Lincoln, though not technically, but in actuality, outlawed slavery. He prevented France and England, getting involved in support of the Confederacy. The Confederacy realized that they must win at all costs, or all would be lost. that is why 1863 and 1864 were such a bloody year. The South was out to win. The Northern politicians and Army Commanders became like sharks with blood in the water.