Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| State\n(class) | Vacator | Reason for change | Successor | Date of successor's\nformal installation |
| --- | --- | --- | --- | --- |
| New Hampshire\n(3) | Vacant | Disputed election. Norris Cotton appointed to seat until special election resolved dispute. | Norris Cotton\n(R) | August 8, 1975 |
| New Hampshire\n(3) | Norris Cotton\n(R) | Successor elected September 18, 1975 | John A. Durkin\n(D) | September 18, 1975 |
| Michigan\n(1) | Philip Hart\n(D) | Died December 26, 1976 | Donald W. Riegle, Jr.\n(D) | December 27, 1976 |
| Missouri\n(1) | Stuart Symington\n(D) | Resigned December 27, 1976 | John Danforth\n(R) | December 27, 1976 |
| Nebraska\n(1) | Roman Hruska\n(R) | Resigned December 27, 1976 | Edward Zorinsky\n(D) | December 28, 1976 |
| Ohio\n(1) | Robert Taft, Jr.\n(R) | Resigned December 28, 1976 | Vacant | Not filled this term |
| Rhode Island\n(1) | John O. Pastore\n(D) | Resigned December 28, 1976 | John Chafee\n(R) | December 29, 1976 |
| Minnesota\n(2) | Walter Mondale\n(DFL) | Resigned December 30, 1976 after being elected Vice-President of the United States. | Wendell Anderson\n(DFL) | December 30, 1976 |
| California\n(1) | John V. Tunney\n(D) | Resigned January 1, 1977 | S. I. Hayakawa\n(R) | January 2, 1977 |
Question:
who resigned his senate seat after being elected vice-president of the united states?
Answer:
Walter Mondale (DFL)