United States House of Representatives elections, 1866
The 1866 elections were a decisive event in the early Reconstruction era, in which President Andrew Johnson faced off against the Radical Republicans in a bitter dispute over whether Reconstruction should be lenient or harsh toward the vanquished South.
Most of the congressmen from the former Confederate states were either prevented from leaving the state or were arrested on the way to the capital. A Congress consisting of mostly Radical Republicans sat early in the Capitol and aside from the delegation from Tennessee who were allowed in, the few Southern Congressmen who arrived were not seated.
Johnson, a War Democrat, had been elected Vice President in the 1864 presidential election as the running mate of Abraham Lincoln, a Republican. (The Republicans had chosen not to re-nominate Hannibal Hamlin for a second term as Vice President).
Lincoln and Johnson ran together under the banner of the National Union Party, which brought together Republicans (with the exception of some hard-line abolitionist Radical Republicans who backed John C. Frémont, who eventually dropped out of the race after brokering a deal with Lincoln) and the War Democrats (the minority of Democrats who backed Lincoln's prosecution of the war, as opposed to the Peace Democrats, or Copperheads, who favored a negotiated settlement with the Confederates).
After the assassination of Lincoln, Johnson became President. He immediately became embroiled in a dispute with the Radical Republicans over the conditions of Reconstruction; Johnson favored a lenient Reconstruction, while Radical Republicans wanted to continue the military occupation of the South and force Southern states to give freedmen (the newly-freed slaves) civil rights (and the right to vote).
Campaign and results 
The Republicans won in a landslide, capturing enough seats to override Johnson's vetoes. Only the border states of Delaware, Maryland, and Kentucky voted for Democrats. Recently Reconstructed Tennessee sent a Republican delegation. The other 10 ex-Confederate states did not vote. As a percentage of the total number of seats available in the House of Representatives, the Republican majority attained in the election of 1866 has never been exceeded in any subsequent Congress. The Democratic Party was able to achieve similar success only in the political environment of the era of the Great Depression in the 1930s.
Election summaries 
Seven former Confederate States were readmitted during this Congress, filling 32 vacancies. There remained 19 vacancies at the end of the 40th Congress, 17 in the three states that had not yet been readmitted, and one each in Georgia and Kentucky. Georgia was readmitted to the House but not to the Senate
|Delaware||At-large||November 6, 1866
|Indiana||District||October 9, 1866||11||8||3||0|
|Iowa||District||October 9, 1866||6||6||0||0|
|Maine||District||September 10, 1866||5||5||0||0|
|Nebraska||At-large||October 9, 1866||1||1||0||0|
|Ohio||District||October 9, 1866||19||16||1||3||1||0|
|Oregon||At-large||June 4, 1866||1||1||0||0|
|Pennsylvania||District||October 9, 1866||24||18||3||6||3||0|
|Vermont||District||September 4, 1866||3||3||0||0|
|West Virginia||District||October 25, 1866||3||3||3||0||0||3|
|California||District||September 6, 1867||3||1||2||2||2||0|
|Connecticut||District||April 1, 1867||4||1||3||3||3||0|
|Kentucky||District||May 4, 1867||9||1||1||7||2||0||4|
|New Hampshire||District||March 12, 1867||3||3||0||0|
|Rhode Island||District||April 3, 1867||2||2||0||0|
|Tennessee||District||August 3, 1867||8||8||8||0||0||8|
|Alabama||District||February 4-8, 1868||6||6||6||0||0|
|Arkansas||District||March 13, 1868||3||3||3||0||0|
|Florida||At-large||May 5, 1868||1||1||1||0||0|
|Georgia||District||April 23, 1868||7||4||4||2||2||0|
|Louisiana||District||April 8, 1868||5||4||4||1||1||0|
|North Carolina||District||April 23, 1868||7||6||6||0||1||1|
|South Carolina||District||April 14-16, 1868||4||4||4||0||0|
|Secessionist States not yet readmitted|
|Texas||District||October 15, 1866||4|
The party affiliations of the 4 Representatives elected in Texas' rejected elections are unknown.
List of races 
|California 1||Donald C. McRuer||Republican||1864||Retired
|Samuel Beach Axtell (D) 57.3%
Timothy G. Phelps (R) 42.7%
|California 2||William Higby||Republican||1862||Re-elected||William Higby (R) 52.1%
James W. Coffroth (D) 47.9%
|California 3||John Bidwell||Republican||1864||Retired
|James A. Johnson (D) 50.6%
Chancellor Hartson (R) 49.4%
Democrats gained one seat this election in Ohio. It was later contested and awarded to the Republican for a net gain of zero.
|Ohio 1||Benjamin Eggleston||Republican||1864||Re-elected|
|Ohio 2||Rutherford B. Hayes||Republican||1864||Re-elected||
|Ohio 3||Robert C. Schenck||Republican||1862||Re-elected|
|Ohio 4||William Lawrence||Republican||1864||Re-elected|
|Ohio 5||Francis C. Le Blond||Democratic||1862||Retired
|Ohio 6||Reader W. Clarke||Republican||1864||Re-elected|
|Ohio 7||Samuel Shellabarger||Republican||1864||Re-elected||
|Ohio 8||James Randolph Hubbell||Republican||1864||Retired
|Ohio 9||Ralph P. Buckland||Republican||1864||Re-elected||
|Ohio 10||James M. Ashley||Republican||1862||Re-elected|
|Ohio 11||Hezekiah S. Bundy||Republican||1864||Retired
|Ohio 12||William E. Finck||Democratic||1862||Retired
|Ohio 13||Columbus Delano||Republican||1864||Lost Re-election
|Ohio 14||Martin Welker||Republican||1864||Re-elected||
|Ohio 15||Tobias A. Plants||Republican||1864||Re-elected|
|Ohio 16||John Bingham||Republican||1864||Re-elected||
|Ohio 17||Ephraim R. Eckley||Republican||1862||Re-elected||
|Ohio 18||Rufus P. Spalding||Republican||1862||Re-elected|
|Ohio 19||James A. Garfield||Republican||1862||Re-elected||
- Excludes states readmitted after the start of Congress
- Including late elections
- Includes 1 Independent Republican and 1 Conservative Republican
- In 1845, Congress passed a law providing for a uniform date for choosing electors. Congressional elections were unaffected by this law, but the date was gradually adopted by the states for Congressional elections
- Previous election had 3 Unionists
- One seat was left unfilled
- Previous election had 4 Unionists
- 8 Unionists in previous election
- After readmission of 7 States
- Both Conservatives
- Previous election had 18 Unionists
- Smith, Joseph P, ed. (1898). History of the Republican Party in Ohio I. Chicago: the Lewis Publishing Company. pp. 228, 229.
- Election contested and seat given to Delano
- Howard K. Beale. The Critical Year (1930)
- Patrick W Riddleberger. 1866, the critical year revisited (1979)
- Hans L. Trefousse. Andrew Johnson: A Biography 1989.
- Edward McPherson, The Political History of the United States of America During the Period of Reconstruction (1875) large collection of speeches and primary documents, 1865–1870, complete text online. [The copyright has expired.]