A bipartisan group of 107 House members has sent a letter to Pres. Clinton urging him to consider the removal of four dams on the lower Snake River in Washington state as a possible means for restoring salmon runs. The letter, from 12 Republicans and 95 Democrats, stresses that the protection of Pacific salmon is a national issue, not just a regional one. The letter marks a significant step in the campaign to remove the dams, which until now has been supported by environmentalists but not many politicians.