The Tenure-of-Office Act furnished the pretext for impeachment. Advised by his Attorney-General that it was unconstitutional, Johnson dismissed the Secretary of War, Edwin M. Stanton, for whose protection the law had been passed. In removing Stanton he broke with Grant, commanding the army, over a question of veracity, and gave to Congress its chance. In February, 1868, the House of Representatives voted to impeach him. The trial of Andrew Johnson before the Senate dragged through April and May. The articles of impeachment were long and detailed in their description of the unquestioned bad manners of the President, but the only specific violation of law cited was in the case of Stanton, and here it could be urged both that the law was unconstitutional and that it was so loosely drawn that it did not really cover this case. In brief, it was the policy of Johnson that was on trial, and it was finally impossible to persuade two-thirds of the Senators that this constituted a high crime or a misdemeanor. The President was acquitted in the middle of May, while the Republican party turned to the more hopeful work of electing his successor. In the fight over Johnson party lines had been strengthened and defined so that no Unionist, not in sympathy with congressional reconstruction, could hope for the nomination. No other issue equaled this in strength. The greenback issue was condemned in a plank that denounced "all forms of repudiation as a national crime," but ran second to the basis of reconstruction. No other candidate than Ulysses S. Grant was considered at the Chicago Convention. Few men have emerged from deserved obscurity to deserved prominence as rapidly as General Grant. In 1861 he was a retired army officer, and a failure. In 1863, as the victor at Fort Donelson and at Vicksburg, he loomed up in national proportions. In the hammering of 1864 and 1865 it was his persistence and moral courage that won the day. In 1868, as commander of the army, and fortunate in his quarrel with Johnson, he was the coveted candidate of both parties, for he had no politics. Held by his associations to the Republican leaders, he was nominated at Chicago on the first ballot, with Schuyler Colfax, of Indiana, as his Vice-President.