US Constitution Series, Amendment XXVII

Amendment XXVII. Congressional Pay Limitation

No law varying the compensation for the services of the Senators and Representatives shall take effect, until an election of Representatives shall have intervened

This prevents Representatives from from voting pay raises for themselves without an intervening election. Of the 435 seats, in a normal election, close to 400 seats are relative safe for incumbents. There are many fewer safe seats this year (maybe 336), but at least if the voters get outraged by a voted pay raise, it has the opportunity to vote the bums out. Senators, apparently because they have the longer six year terms, are no so handicapped.