In 1866, the Republican Party had 173 seats in the House of Representatives. The Democrats had 47. The Republicans had 57 seats in the Senate. The Democrats had 9. In 1868, the Republicans lost only two seats in the House, and gained five in the Senate, while the Democrats gained a mere 20 seats in the House and 3 in the Senate.
That's overwhelming control of the government. Remember, the Senate is also a pretty good proxy for State government control at this time, since senators are elected by state legislatures.
Just over three fourths of the House (78.6%), though I agree on the Senate.
And a change of twenty out the House's 220 seats is not minimal. Though if this is 20 total, I suppose...I don't have a list of the make up of Congress handy at the moment.
If you want to say someone has near absolute control, you'd need to have opposition percentages measured in single digits. Not trying to nitpick, but three-fourths - while impressive - is not total control, either, especially with any meaningful division within the group in question. And the Republicans seem to have had a gap between the radicals (small R - the big R radicals count but they're not the only examples) and industrial/capitalists.
They failed to get Andrew Johnson impeached because Republicans balked at the precedent it would set in turning impeachment into a political tool to be exercised over the executive. The conviction failed by one vote in the Senate. Throughout this period, the Democrats only could muster token opposition, as the Republicans had more than 2/3rds control of both Houses, and a supermajority of state governments under their control (hence the quick passage of the 13th, 14th and 15th Amendments).
Which period are we talking about? By 1873, the Radicals are on their way to being tarred with the slander that has dominated the telling of Reconstruction for most of the period between its end and the present.
And of course, this is assuming that the Republicans are all for the same things, which is not the case. Sometimes, but probably not to the point where they would be able to use that to do more than they did.
What I meant was that Reconstruction was begun to obliterate the socio-economic system that had sustained the elite Southern planter class. The Republicans, particularly the Radical faction which was dominant at the time, were going to drag the South kicking and screaming into the 19th century whether they wanted it or not. That meant undoing the plantation economy and paving the way for industrial capitalism.
They failed, but not for lack of trying. The political will to keep Reconstruction going could not be sustained forever, especially under the mechanics of the Constitution.
Failing for reasons other than lack of trying is very strongly telling about how much actual power they had and how dominant the Radicals really were, however. They had eight years and thanks to facing terrorism in the South and apathy in the North, well, we don't see equal rights for century.
Changing the Constitution wouldn't do much to adjust that, unfortunately.