BOB DOLE and Alan Simpson, who were elected Senate Republican leader and whip yesterday, have much in common. Neither is in the tradition of those who have seen -- and achieved -- legislative leadership roles as a kind of alternative to heavy involvement in specific substantive issues. This is the tradition of facilitators, of legislators who decided early that they would not be strongly identified with any particular side in an internal dispute, but would instead be part of the working machinery. Sens. Dole and Simpson, on the contrary, have been anything but neutral or detached on questions of substance.

Sen. Simpson made a sustained and heroic effort in the last Congress to get much needed immigration reform enacted and, against great odds, almost succeeded. He has also built a solid reputation -- in both houses of Congress -- as a person who can work out sensible compromises on other red-hot issues, such as nuclear waste disposal, Agent Orange compensation and Superfund. Sen. Dole, as chairman of the Finance Committee and an active member of the Judiciary and Agriculture committees, has been a major architect of almost every piece of legislation passed in the last four years, including tax, Social Security and bankruptcy law reform and renewal of voting rights and farm legislation.

Not that either man lacks the talents essential to congressional leadership -- far from it: the centrist Republican Senate establishment, presided over until now by Howard Baker, has been, arguably, the most effective and responsible governing instrumentality in town these past four years. With Sens. Dole and Simpson in leadership positions, it is unlikely that the White House will have any opportunity to duck the large issues of the next four years. While the Democrats smart from their lopided defeat in the presidential race, there is much talk of congressional stalemate. But House Democrats, at least for the past 30 years, have no tradition of dogged opposition to explicit and strongly backed proposals of a Republican president when these are also supported by his party in Congress. The success of President Reagan's 1981 tax and budget proposals is a case in point.

The difficulty has come when, as in the past three years, the president has either floated plans that were so unrealistic as to be disregarded by his own congressional leaders or has expected a divided Congress to work out a compromise and persuade him to accept it. Sens. Dole and Simpson are tough, realistic men. They have to keep an eye on the vulnerability of Republican senators in the 1986 elections as well as on the future of the presidency when Ronald Reagan leaves office. They will probably give the president all the support he needs to put through a sensible program, even one that requires much political courage. But we expect they will not take kindly to being sent on a Mission Impossible.

Sens. Dole and Simpson, by the way, have something else in common. They are, if not Capitol Hill's two funniest men, at least among the top five. (We mean intentionally funny, as distinct from the other kind, which abounds up there.) The Democrats, lacking what you could call photogenic -- not to say charismatic -- leadership in Congress and being without national leadership anywhere else, are not going to profit from the emergence of these two as national spokesmen.