Maybe it's the soggy economy. Or perhaps it's the public's sour mood toward politicians. But the Federal Election Commission reports that, during the first six months of 1993, campaign funds raised by Senate candidates declined for the first time in six years. The $25 million raked in by candidates for the 34 Senate seats up next fall is down 25% from the take two years ago and down 15% from the same period in 1989. As usual, powerful incumbents are scarfing up the lion's share of the money. Finance Committee Chairman Daniel Patrick Moynihan (D-N.Y.), for example, has $1.5 million on hand--with no challenger in sight. But some challengers are doing well, too. In Arizona, Republican Representative Jon Kyl has raised more than his Democratic opponent, embattled incumbent Dennis DeConcini. And Representative Jim Cooper (D-Tenn.) has a $1 million war chest, 13 times as much money as appointed Democratic Senator Harlan Mathews, who has not yet declared whether he'll seek another term.