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 (class) | Vacator | Reason for change | Successor | Date of successors formal installation |
| --- | --- | --- | --- | --- |
| Maryland (3) | Vacant | Sen. Thomas H. Hicks died during previous congress | John Creswell (UU) | March 9, 1865 |
| New Jersey (2) | Vacant | Presented credentials as Sen-elect | John P. Stockton (D) | March 15, 1865 |
| Tennessee (2) | Vacant | Tennessee re-admitted to the Union | Joseph S. Fowler (UU) | July 24, 1866 |
| Tennessee (1) | Vacant | Tennessee re-admitted to the Union | David T. Patterson (U) | July 28, 1866 |
| Vermont (3) | Jacob Collamer (R) | Died November 9, 1865 | Luke P. Poland (R) | November 21, 1865 |
| Vermont (1) | Solomon Foot (R) | Died March 28, 1866 | George F. Edmunds (R) | April 3, 1866 |
| New Jersey (1) | William Wright (D) | Died November 1, 1866 | Frederick T. Frelinghuysen (R) | November 12, 1866 |
| Nebraska (1) | New seat | Nebraska admitted to the Union March 1, 1867. | Thomas Tipton (R) | March 1, 1867 |
Question:
What was the reason for change in staff in formal installations on March 15, 1865?
Answer:
Presented credentials as Sen-elect