The 1978 United States Senate elections were held on November 7, in the middle of Democratic President Jimmy Carter's term. The 33 seats of Class 2 were contested in regular elections. Special elections were also held to fill vacancies.

Thirteen seats changed hands between parties, resulting in a net gain of three seats for the Republicans allowing them to break the Democrats' filibuster-proof majority. Democrats nevertheless retained a 58–41 majority.

Results summary + ↓ 58 1 41 Democratic I Republican

Parties Total Democratic Republican Independent Other Last elections (1976)Before these elections 61 38 1 0 100 Not up 43 21 1 0 65 Up 18 17 0 — 35 16 17 — — 33 1 — — — 1 1 — — — 1 Incumbent retired 5 5 — — 10 2 3 — — 5 2 Republicans replaced by 2 Democrats 3 Democrats replaced by 3 Republicans — — 5 Result 4 6 — — 10 Incumbent ran 13 12 — — 25 6 9 — — 15 2 Republicans replaced by 2 Democrats 5 Democrats replaced by 5 Republicans — — 7 2 0 — — 2 1 Republican replaced by 1 Democrat — — 1 Result 11 14 0 0 25 Total elected 15 20 0 0 35 Net gain/loss 3 3 3 Nationwide vote 15,302,929 14,794,225 299,624 278,078 30,674,856 Share 49.89% 48.23% 0.98% 0.91% 100% Result 58 41 1 0 100

Source: Clerk of the United States House of Representatives

Gains, losses, and holds Retirements Five Republicans and three Democrats retired instead of seeking re-election. One Democrat retired instead of seeking election to finish the unexpired term and one Democrat retired instead of seeking election to a full term.

StateSenatorReplaced by Alabama (regular) Arkansas Kansas Minnesota (special) Mississippi Nebraska Oklahoma South Dakota Virginia Wyoming

Defeats Three Republicans and four Democrats sought re-election but lost in the primary or general election. One Democrat sought election to a full term but lost in the general election, one Democrat sought election to a full term but lost in the primary and one Democrat sought election to finish the unexpired term but lost in the primary.

StateSenatorReplaced by Alabama (special) Colorado Iowa Maine Massachusetts Michigan Minnesota (regular) Montana New Hampshire New Jersey

Post-election changes One Democrat resigned on May 7, 1980, and was later replaced by Democratic appointee.

StateSenatorReplaced by Maine(Class 1)

Change in composition Before the elections D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D Majority → D D D D D D D D D D D I R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R

After the elections

D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D Majority → D R I D D D D D D D R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R Key D Democratic R Republican I Independent

Race summary Special elections during the 95th Congress In these special elections, the winner was seated during 1978 or before January 3, 1979; ordered by election date, then state.

State Incumbent Result Candidates Senator Party Electoral history Alabama(Class 3) Maryon Pittman Allen Democratic 1978 Interim appointee lost nomination.Democratic hold. Minnesota(Class 1) Muriel Humphrey DFL 1978 Interim appointee ineligible to run.Republican gain.

Elections leading to the next Congress In these general elections, the winners were elected for the term beginning January 3, 1979; ordered by state.

All of the elections involved the Class 2 seats.

State Incumbent Result Candidates Senator Party Electoral history Alabama Democratic 1946 19481954196019661972 Incumbent retired.Democratic hold. Alaska Republican 1968 19701972 Incumbent re-elected. Arkansas Democratic 1977 Interim appointee retired.Democratic hold. Colorado Democratic 1972 Incumbent lost re-election.Republican gain. Delaware Democratic 1972 Incumbent re-elected. Georgia Democratic 1972 1972 Incumbent re-elected. Idaho Republican 1972 Incumbent re-elected. Illinois Republican 19661972 Incumbent re-elected. Iowa Democratic 1972 Incumbent lost re-election.Republican gain. Kansas Republican 1962 1962 19661972 Incumbent retired.Republican hold.Incumbent resigned December 23, 1978 to give successor preferential seniority.Successor appointed December 23, 1978. Kentucky Democratic 1972 Incumbent re-elected. Louisiana Democratic 1972 1972 Incumbent re-elected. Maine Democratic 1972 Incumbent lost re-election.Republican gain. Massachusetts Republican 19661972 Incumbent lost re-election.Democratic gain. Michigan Republican 1966 19661972 Incumbent lost re-election.Democratic gain. Minnesota DFL 1976 Interim appointee lost election.Republican gain.Incumbent resigned December 29, 1978 to give successor preferential seniority.Successor appointed December 30, 1978. Mississippi Democratic 194219481954196019661972 Incumbent retired.Republican gain.Incumbent resigned December 27, 1978 to give successor preferential seniority.Successor appointed December 27, 1978. Montana Democratic 1978 Interim appointee lost nomination.Democratic hold.Incumbent resigned December 12, 1978 to give successor preferential seniority.Successor appointed December 15, 1978. Nebraska Republican 1954196019661972 Incumbent retired.Democratic gain. New Hampshire Democratic 1962 19661972 Incumbent lost re-election.Republican gain. New Jersey Republican 1954196019661972 Incumbent lost renomination.Democratic gain. New Mexico Republican 1972 Incumbent re-elected. North Carolina Republican 1972 Incumbent re-elected. Oklahoma Republican 1972 Incumbent retired.Democratic gain. Oregon Republican 19661972 Incumbent re-elected. Rhode Island Democratic 196019661972 Incumbent re-elected. South Carolina Republican 1954 (write-in)1954 1956 1956 196019661972 Incumbent re-elected. South Dakota Democratic 1972 Incumbent retired.New senator elected.Republican gain. Tennessee Republican 19661972 Incumbent re-elected. Texas Republican 1961 19661972 Incumbent re-elected. Virginia Republican 1972 Incumbent retired.Republican hold.Incumbent resigned January 1, 1979 to give successor preferential seniority.Successor appointed January 2, 1979. West Virginia Democratic 1958 196019661972 Incumbent re-elected. Wyoming Republican 19661972 Incumbent retired.Republican hold.Incumbent resigned December 31, 1978 to give successor preferential seniority.Successor appointed January 1, 1979.

Closest races Nine races had a margin of victory under 10%:

State Party of winner Margin Virginia Republican 0.38% Texas Republican 0.53% West Virginia Democratic 0.96% New Hampshire Republican (flip) 2.20% Iowa Republican (flip) 3.21% Michigan Democratic (flip) 4.29% New Mexico Republican 6.82% Illinois Republican 7.87% North Carolina Republican 9.02%

Oklahoma was the tipping point state with a margin of 32.6%.

Alabama

There were two elections in Alabama, due to the death of senator Jim Allen.

Alabama (regular)

Democrat John Sparkman retired and was succeeded by Howell Heflin, the former chief justice of the Supreme Court of Alabama. Heflin, the Democratic candidate, faced no Republican opponent in the general election, defeating Prohibition Party nominee Jerome B. Couch.

Alabama (special)

Following the death of senator Jim Allen, his widow Maryon was appointed by governor George Wallace to fill the vacancy until a special election could be held. In this election, Democratic state senator Donald W. Stewart defeated former Republican congressman James D. Martin to serve the remaining two years of the term.

Alaska

Republican Ted Stevens won reelection to a second full (his third total) term, defeating Democrat Donald Hobbs.

Arkansas

Following the death of senator John L. McClellan, then Kaneaster Hodges Jr. was appointed by governor David Pryor to fill the vacancy until a special election could be held. In this election, Democratic state governor David Pryor defeated former Republican challenger Thomas Kelly Jr. to serve the six-year term.

Colorado

Democrat Floyd Haskell decided to run for re-election to a second term, but was defeated by William L. Armstrong, the Republican nominee and the U.S. Representative.

Delaware

Democratic United States senator Joe Biden won re-election to a second term, defeating Republican challenger James H. Baxter Jr., the Delaware Secretary of Agriculture.

Georgia

Democrat Sam Nunn won re-election to a second term.

Idaho

Republican James A. McClure was elected to a second term in office.

Illinois

Republican Charles H. Percy ran for re-election to a third term in the United States Senate. Percy was opposed by Democratic nominee Alex Seith (D), attorney and former member of the Cook County Zoning Board of Appeals. Though Percy had been expected to coast to re-election over Seith, a first-time candidate, the election quickly became competitive. In the last few days of the campaign, a desperate Percy ran a television advertisement that featured him apologizing and acknowledging that, "I got your message and you're right." Percy's last-ditch effort appeared to have paid off, as he was able to edge out Seith to win what would end up being his third and final term in the Senate.

Iowa

Democrat Dick Clark decided to run for re-election to a second term, but was defeated by Roger Jepsen, the Republican nominee and former Lieutenant Governor of Iowa.

Kansas

Republican James B. Pearson retired and was succeeded by Nancy Kassebaum, the daughter of Alf Landon, defeating Democratic nominee William R. Roy, the former U.S. Representative. Roy also lost to Bob Dole in the 1974 election for Kansas' other Senate seat.

Kentucky

Democrat Walter Huddleston was re-elected to a second term.

Louisiana

Democrat J. Bennett Johnston won re-election to unopposed and his second term.

Maine

Democrat William Hathaway decided to run for re-election to a second term, but was defeated by William Cohen, the Republican nominee and the United States Congressman from Maine's 2nd congressional district and Hayes Gahagan, former Maine State Senator

Massachusetts

Republican Edward Brooke was defeated by Democratic congressman Paul E. Tsongas.

Michigan

Republican Robert P. Griffin ran for re-election to a third term, but was defeated by the Democratic candidate, and former Detroit City Council President Carl Levin.

Minnesota

There were two elections in Minnesota, due to the death of Hubert Humphrey.

Minnesota (regular)

Democrat Wendell Anderson was defeated by Republican challenger businessman Rudy Boschwitz.

In 1978, all three key statewide races in Minnesota were up for election—the Governorship, and both Senate Seats (the other Senate seat belonged to Hubert Humphrey, who died in 1978). But, there was a particular oddity to the three races—all three had incumbents who were never elected to the office in the first place. This became a well played issue by the Republicans—a billboard put up across the state read, "The DFL is going to face something scary -- an election".

When Walter Mondale resigned after being elected to the Vice Presidency in 1976, sitting Governor Wendell Anderson resigned in order to be appointed by his successor Rudy Perpich to the open seat. This act did not sit well with the electorate. Plywood magnate Rudy Boschwitz campaigned as a liberal Republican and spent freely of his own money, but all that seemed to really matter was that he was neither a DFLer or Wendell Anderson in an election cycle where both were rejected by the voters. The result was not even close—the challenger Boschwitz won in a 16-point landslide as all three statewide offices switched into Republican hands.

Minnesota (special)

Incumbent Muriel Humphrey retired. Democratic candidate Bob Short was defeated by Republican candidate David Durenberger.