Members of the Democratic party have called him the worst President we've ever seen and said that history will judge him harshly for the way in which he has abused power. They have called him a despot, and, in effect, a fascist. They have railed against him for starting a bloody and unnecessary war, which they have called a "failure." They have been critical of what they thought were mistakes in the way the war was conducted. They have accused the President of starting the war over commercial interests rather than over national security. They have criticized the President for illegally overextending the powers of the Presidency, spending money without authorization, telling his generals how to fight the war, unlawfully imprisoning people and mistreating prisoners. They complain that people who criticize the administration are accused of being treasonous or of undermining the war effort. They have been aghast at his use of military tribunals to deal with Americans who he suspected were working for the enemy. When a military veteran ran against him in the contest for his second term in office he was accused of being a chickenhawk who committed people to fight a war when he had never done so himself (even though he served in the state militia he never saw combat.)
This was, of course, President Abraham Lincoln.
Lincoln went a little further than that, though:
Lincoln's policy was to have treasonous federal lawmakers arrested and tried before military tribunals, and exiled or hanged if convicted. Treason, in Lincoln's view, included criticizing his administration on the conduct of the war.
Lincoln had tens of thousands of political opponents in the North arrested, including dozens of opposition newspaper editors.
In one case he had a congressman from Ohio, Clement L. Vallandigham, arrested, tried in a military tribunal, and deported. The congressman's treason was to criticize Lincoln from the floor of Congress for abuse of power.
Lincoln also considered arresting a member of the Supreme Court. So, Lincoln basically intimidated critics in Congress and in the Court into silence for the duration of the Civil War.
It appears that the northern Democrats critical of Lincoln had some legitimate beefs. It's hard to find that out by reading most history books today, though, which should give Democrats today, who are confident that history will see Bush the way they do, some pause.