Senators are not "elected", as such, they are appointed. So no one pays for their elections. Their salaries and other expenses are paid out of the general tax funds.
However, this answer is going to come as a surprise to voters, as they do have elections every 6 years.
The seventeenth amendment addressed the issue and process of the election of the US senators.
All members of the House of Representatives and the Senate are paid in full by the U.S. Treasury, which ultimately gets its money from the tax payers.
the us government and their salary is set by the law
Bill Nelson (D) and Marco Rubio (R) are the U.S. Senators representing Florida. Nelson's next election will be in 2018. Rubio's next election will be in 2022.
Edward Markey (D) and Elizabeth Warren (D) are the U.S. Senators representing Massachusetts. Warren's next election will be in 2018. Markey's next election will be in 2020.
Re-election.
Private donations, Business donations, fund raising events, and special interest groups help pay for the process of being elected, otherwise, income tax pays them.
The provisions of the seventeenth amendment were that the U.S. senators would be elected by the people.
Dean Heller (R) and Catherine Cortez Masto (D) are the U.S. Senators representing Nevada. Heller's next election will be in 2018. Masto's next election will be in 2022.
Every state has 2 U.S. Senators in the U.S. Senate. Amy Klobuchar (D) and Alan Franken (D) are the U.S. Senators representing Minnesota. Klobuchar's next election will be in 2018. Franken's next election will be in 2020.
All U. S. states have 2 U.S. Senators. Thomas Carper (D) and Chris Coons (D) are the U.S. Senators representing Delaware. Carper's next election will be in 2018. Coon's next election will be in 2020.
Idaho has 2 U.S. Senators. Michael Crapo (R) and James Risch (R) are the U.S. Senators representing Idaho. Crapo's next election will be in 2022. Risch's next election will be in 2020.