Lincoln opposed Mr. Douglas in 1858 when he contested the latter's reelection to the United States Senate. Toward this end he launched a more determined antislavery program than ever before, advancing the doctrine that "a house divided against itself cannot stand" and likewise that "the Union could not endure permanently, half slave and half free."[9] He further declared that either the advocates of slavery would push the institution forward until it became alike lawful in both North and South, or the opponents thereof would arrest its extension. Douglas had charged the Republicans with the intent to abolish slavery in the States and had asserted that their opposition to the Dred Scott decision marked their desire for Negro equality and amalgamation.[10] To this charge Lincoln replied that the Republicans were not directing their efforts toward abolition in the slave States, but toward the exclusion of slavery from the territories. He forcibly denied the accusation that the Republicans solicited social equality and amalgamation with the Negro, declaring that there was a physical difference between the two races, which probably would forever forbid their living together on equal footing; and that, inasmuch as it became a necessity that there must be a difference, he, like Douglas, favored his race for the superior position. Lincoln admitted that in some respects the Negro, according to the Declaration of Independence, was not the white man's equal; that in color, size, intellect, moral development, or social capacity the Negro was not on a par with the white man; but that that instrument did, with tolerable distinctness, consider "all men created equal" with certain inalienable rights, such as "life, liberty, and the pursuit of happiness."[11] Lincoln held that, notwithstanding all these facts, there was no reason why the Negro was not entitled to all the natural rights embraced by the Declaration of Independence, which are enjoyed by the white man.[12] He interpreted the standard maxim that "all men are created equal" as being of no practical use in effecting the separation of the thirteen Colonies from Great Britain, and, on the contrary, contended that it was placed in the Declaration of Independence for future use in the attainment of democracy. Lincoln failed to defeat Douglas for the United States Senate but he continued to discuss the constitutionality of the restriction of slavery. On more than one instance he limited his remarks to this question, irrespective of the type of his audience or character of the occasion. He persistently reiterated the doctrine that there was no provision in the Constitution that precluded the right of the Federal Government to control slavery in the territories.[13]