Although he never officially held any office, he rose to prominence as a member of President Andrew Jackson’s "Kitchen Cabinet". After he publicly supported President Jackson's opposition to the nullification movement, he was invited to leave his native Kentucky and establish a Democratic newspaper in Washington, DC. That paper, the "Washington Globe", became recognized as the mouthpiece for the Democratic Party. He served in that capacity until 1845, when President James K. Polk removed him for agitating against any War with Mexico despite the protest of Jackson and other prominent Democrats. He continued to support the Democratic Party, backing former President Martin Van Buren's 1848 re-election attempt, and being instrumental in the election of President Franklin Pierce in 1852. When the Missouri Compromise of 1820 was repealed in 1854, he left the Democratic Party in favor of the fledgling Republican Party. His prominence in the new political party was such that he chaired both the 1856 and 1860 Republican Conventions, and exerted great influence in the nomination of Abraham Lincoln as the Party's presidential candidate. After the Civil War started with the bombardment of Fort Sumter, South Carolina in April 1861, he was detailed by President Lincoln to feel out Colonel Robert E. Lee's position on the conflict, and to see how favorably he would be to an offer to lead the Union forces against the Confederacy (he was not officially offered the command, contrary to popular myth). In 1864 Francis P. Blair Sr. took it upon himself to pass through Confederate lines to meet with Confederate President Jefferson Davis in a desire to see if peace could be obtained. His unauthorized meetings led to the unsuccessful "Peace Conference" of February 1865. After the war's end and the assassination of President Lincoln, he supported Lincoln's moderate policies of reconstruction, and opposed the harsh measures that were actually implemented. This alienated him from the leaders of the Republican Party, and he aligned himself with the Democrats again until his death in 1876. Two of his sons rose to prominence during the Civil War. Elder son Montgomery Blair served as President Lincoln's Postmaster General from 1861 to 1864, and younger son Francis P. Blair Jr. rose to a Major General of Volunteers in the Union Army.