Montgomery Blair came to prominence in the Dred Scott case. Dred Scott was a slave who was taken north of the line established in the Missouri Compromise. North of this line slavery was illegal - south of it, slavery was legal. Dred Scott had gone back south with his master and then sued, saying that his slavery had ended as soon as he had crossed the line. Montgomery Blair was Scott's lawyer and argued his case before the Supreme Court. Chief Justice Roger Brooke Taney from Maryland proclaimed in the Dred Scott decision 'that blacks, not just slaves but free blacks as well were not citizens of the United States and could 'therefor claim none of the rights and privileges which the Constitution provides'.. Congress did not have the power to prohibit slavery anywhere in the United States or the territories. This invalidated the Missouri Compromise and rapidly increased tensions in both the North and the South. Many Democrats discontented with their party's liberal view on slavery, severed their political affiliations with the Democrats and aligned with the new anti-slavery Republican party in 1856.
As the 1860 election heated up, the Blair family found themselves in a critical place in the Republican party. Montgomery Blair controlled the delegates from Maryland, his brother, the delegates from Missouri. The Blairs' threw their support to Lincoln. In exchange for this, Lincoln appointed Montgomery Blair Postmaster General (one of the most important positions in the government at that time).
Blair and his family pursued an abolitionist policy that earned them the hatred of the South, to the extent that they launched a special raid to burn down the family home.
In 1864 with the fall elections rapidly approaching the Republicans were worried about the slow progress of the war and the internal strife within the Cabinet since the resignation of the Secretary of the Treasury Salmon P. Chase had been accepted. Many people felt that if Lincoln were to replace his Secretary of War Edwin M. Stanton he would improve his chances at re-election. Lincoln in order to satisfy the radical republicans still hurting at Chase's dismissal sacrificed Montgomery Blair. The radicals concluded that Lincoln was their lone hope.
After the war Blair went back to the Democratic Party and supported their platforms in supported Democratic party, 1868, 1872, 1876.
He died July 27, 1883.
The Blair home, across the from the White House, was purchased by the United States Government in 1942 and is now used to house high-ranking foreign visitors.
Bibliography: W. E. Smith, "Montgomery Blair" John Niven "Salmon P. Chase"