IT IS LOOKING more and more as if the Republicans will be lucky to maintain control of the Senate after next year's elections. Almost everything seems to be conspiring against them. A majority--19 of 33--of the Senate seats up in 1984 are held now by Republicans, and so they have more at risk. About half the Democrats' seats are held by moderate southerners, who seem unlikely in most cases to be seriously challenged. But many of the Republican seats are held by men who can be described charitably as less than the best their party has to offer. Republican incumbents currently trail in polls in North Carolina and Iowa--a sure sign of trouble--and appear weak in several other states.

And even the seats of some of the most talented Republicans are in jeopardy. Howard Baker, who has done a remarkable job as majority leader, would almost surely have won reelection in Tennessee, had he run. But he chose to retire--a decision that, in this era of three-year campaigns, positions him to run for president in 1988. Last week, John Tower, the four-term incumbent from Texas, also announced his retirement. He was not a sure bet for reelection, but he was almost surely the strongest Republican candidate.

Tennessee and Texas are states whose Democratic tradition goes back not only to Reconstruction but to the state's founding heroes, Andrew Jackson and Sam Houston. In Tennessee, Democratic Rep. Albert Gore Jr. seems far ahead already; like Sen. Baker, he is a talented and thoughtful member of a prominent political family. In Texas, the Republicans may produce a strong candidate, possibly Phil Gramm, who until last winter was a Boll Weevil Democrat. But the Democrats have at least three strong candidates vying for their nomination, and recent trends, apparent in the 1982 results, tend to favor them.

It will be ironic if the Republicans lose the Senate, because by all but the most partisan of standards, they have done a good job of running it these past three years. They have dispatched business about as promptly as possible, given the Senate's rules; they have taken the initiative responsibly and at some political risk, as on the 1982 tax bill; they have put on the back burner many issues that belong there. Their leaders have often been brilliant, and their backbenchers have been suitably quiet. They have certainly been more unified than Senate Democrats in recent Congresses. Should they lose control, it will be less from the merits than from bad luck--for which the consolation (and a very small one to them) will be that extraordinary good luck helped secure their majority in 1980.