To most political observers it is almost tries to assert that Massachusetts is one of the most liberal states in the nation. One only has to mention the reception former Sen. George McGovern (D-S.D.), victim of a landslide defeat in the 1972 presidential election, received here after the election. "Nixon 49, America I" the buttons of cheering supporters read, proudly boasting that the Commonwealth was the only state that voted for the liberal Democrat.

One only has to note the reputation of the state's current leading political figures. Senior Sen. Edward M. Kennedy '54, and Rep. Thomas P. O'Neill Jr. speaker of the House, both appear to many as archetypal New Deal politicians. Junior Sen. Paul Tsongas is jockeying with other young Democrats to lead the "New Liberalism."

But Massachusetts state politics are more complex, "full of seeming paradoxes" the 1982 Almanac of American Politics says. Just look at Democratic Gov. Edward J. King. Since taking office four years ago, his primary goal has been to enhance the state's business climate. King regularly consults a panel of business representatives when making major decisions. He has worked in the past at loosening environmental regulations, has strongly pushed for nuclear energy, and twice vetoed a bill imposing a deposit on beer and soft drink bottles. To trim the budget. King has cracked down on welfare cheats, made welfare qualifying requirements tougher and proposed a now-revised "workfare" plan which originally would have forced welfare recipients to put in some time working for the government.

One of the few Democratic governors to endorse President Reagan's budget cuts last year, King remains one of the small number of governors of either party to back the President. While more and more loyal Republican executives are questioning the effect of the New Federalism on the states, King remains a consistent friendly visitor to the White House.

In this election year, the governor is determined to prove that his 1978 success was no fluke, and that his conservative policies accurately represent the desires of "common people."

Tough challenger and former Gov. Michael S. Dukakis (King's victim in the "primary blizzard of 1978") currently leads in the polls. King has so far dominated the tone of the campaign, setting the agenda for debate. And he has focused attention on one of the conservatives' favorite issues--taxation.

Taxes are nearly all King will talk about. With proposals flying back and forth to arrange a gubernatorial race public debate. King has insisted that at least for the first session of a series of debates, he will only discuss taxes. Almost all of the $200,000 that "Friends of Ed King" spent on airtime in January bought 10 to 60 second spots focusing on the "high taxes" Dukakis generated during his reign, and on the "relief" King has provided in the past three years. The most casual radio listener or television viewer must now be familiar with what King calls the "Dukakis surtax."

King's tack so far has been rather simple While singling out the 7.5 percent surtax Dukakis imposed on income taxes to pull the state out of its fiscal crisis. King has taken credit for significantly reducing the remaining tax burden for state residents. In his State of the State address in early January, he boldly declared that "Taxachusetts is dead," claiming that taxes have decreased since 1978 by $30 per $1000 of earned income.

A week later, in his financial message. King took credit for a $100 million budget surplus and promised to provide further tax cuts by completely eliminating the "Dukakis surtax."

Some observers are more skeptical about what King has actually accomplished so far, and about his continued performance in a second term. The last time he hit the campaign trail. King pledged $500 million in immediate property tax reductions. Unable to deliver on that promise, he did succeed in leading a bill through the legislature imposing a cap on the amount local governments could increase property taxes. But several communities took advantage of the override provisions in the bill, and the ensuing increase in local taxes spurred the passage of Proposition 2 1/2, the property tax reducing referendum King first opposed but now accepts.

Many challenge King's assertion that state and local governments are now taking a smaller bite out of personal income. They note that several public service fees have increased concurrently with property tax reductions. Auto registration, drivers' license and car inspection fees have all doubled, while MBTA fares have tripled.

But King's defenders stand by his record, and will probably continue with the current strategy of pounding on the tax issue until it sticks in the mind of the electorate, figuring that "Dukakis surtax" is much easier to remember than comparative budgetary statistics.

King's staff hopes soon to move on to the issue of crime prevention, where they say the incumbent has a much tougher reputation than his predecessor. And by September 14, they hope that Democratic voters will believe that King best represents the economic interests of the working class.