Should US Senators and US Congressmen have to resign their seats to run for President?

We have been paying three of our US Senators for well over one year for doing a job that they can't and are not doing because they have been campaigning for President. These are McCain, Obama, and until recently, Clinton. I am of the opinion that we should require our Senators and/or Congressmen to resign their seats if they are involved in an active campaign for say six months. If a person thinks he is a serious contender for President, they shouldn't keep their legislative seats inactive so they can fall back on them if they fail in their attempt. Governors should be up to their States, they at least have a Lieutenant Governor to fill in for them while they are away. The only person that did this to my knowledge is Bob Dole, and I think it was the right thing to do. Vice President canidates need not be included because their campaign time is short, except in cases like say Obama picked Clinton who already had been involved for more than a year.