After you work for a while in Washington you begin to wonder about the American political system. We have just had an election in which the President got a ''landslide,'' but did not get a solid legislative mandate in the parliamentary sense. Ambiguity seems built into our government.Take as a parallel the unlikely issue of gun control. If ever there were a ''mandate'' it is that Americans want something done to reduce the nation's high crime rate. Yet, the political debate about how to lower it goes on and on. The problem is outlined anew in a carefully reasoned article by Jervis Anderson in The New Yorker of Nov. 12. Is there a connection between the high murder rate in America and the ease of buying handguns? Mr. Anderson reviews all the old arguments and makes his views clear, but does not hand down a formal indictment. Yet it is clear that the murder rate in the US is shocking. In almost no other part of the world are civilians as free to use guns. He notes that ''no major political office anywhere has lost so many of its occupants to civilian gunfire as the presidency of the United States, nor have other world leaders been shot at as frequently by the citizens of their own nation.''It is estimated that there are 60 million handguns loose in the country. In 1980 alone about 21/2 million handguns were made and sold in the US, and about a quarter of a million more were assembled here from imported parts. The Vietnam war took 46,121 American lives between 1963 and 1973. During the same years within the US, an estimated 84,644 civilians died from the use of firearms. The murder rate in the US exceeds that of any other advanced society in the world.Congress passed the restrictive National Firearms Act in 1934 and went further in 1938 by enacting the Federal Firearms Act. This ushered in a mild form of federal gun control. Five years after John F. Kennedy's assassination, Congress got around to enacting the Gun Control Act of 1968. There is a powerful gun lobby that opposes federal handgun controls. At the moment two major gun proposals are pending, one cosponsored by Sen. Edward Kennedy (D) of Massachusetts and Rep. Peter Rodino (D) of New Jersey. Both men would tighten existing controls. But unfortunately, that's not the end of the debate. Bills have been introduced by Sen. James McClure (R) of Idaho and Rep. Harold L. Volkmer (D) of Missouri which would loosen gun control. The latter is supported by the National Rifle Association, one of the most effective lobbies in Washington.President Reagan does not like federal gun control legislation and is warmly supported by the National Rifle Association. Instead, he favors tougher sentences for criminals who use guns in committing a crime. Presumably, he will name Supreme Court justices who agree with this interpretation. He promised a gathering of 4,000 NRA members last year that he would sign the McClure-Volkmer bill if it's enacted by Congress. He continued, ''It does my spirit good to be with people who never stop believing in the future, and who never back down one inch from defending the constitutional freedoms that are every American's birthright!'' He added, ''It is a nasty truth, but those who seek to inflict harm are not fazed by gun-control laws.'' He praised the NRA, saying that no group does more ''to promote gun safety and respect for the laws of this land.'' He declared that locking ''the hard-core criminals up, and throwing away the key, is the best gun-control law we could ever have.''Ironically, spectators had to walk past metal detectors to hear Mr. Reagan deliver his attack on gun control.