For those who love the mysterious ways in which politics deals with the conflicts of personalities, parties and principles, Bradley International Airport has been a Mecca this year.

On a weekend in May, I flew into Bradley and headed 45 minutes up Interstate 91 to Springfield, where the Massachusetts Democratic convention was sitting in judgment on the political future of Gov. Edward J. King.

Last weekend, it was back to Bradley again, this time turning south on 91 for the half-hour drive into Hartford, where the Connecticut Republican convention was passing judgment on Sen. Lowell P. Weicker Jr.

There is a world of difference between the two-term senator from Connecticut and the one-term governor of Massachusetts. But they have one thing in common: their careers may be in trouble because they have dared to defy the orthodoxies of their own parties.

Weicker was under fire because, in the home base of George Bush, he has made a habit of denouncing and opposing the policies of the Reagan-Bush administration. King was under fire because, in the home base of Ted Kennedy, he has made a habit of praising and emulating those same Reagan policies.

Former Democratic governor Michael S. Dukakis challenged King for the party's endorsement with the boast that he would "not be Ronald Reagan's favorite governor." Prescott Bush Jr., the vice president's brother, challenged Weicker for the party's endorsement with the claim that he, Bush, would strive to be Reagan's most loyal senator.

Weicker was indicted on the charge that he rejects the conservative faith in deep tax cuts and budget cuts, bigger defense outlays and constitutional amendments on abortion, busing and school prayer. King supports everything Weicker opposes. He was indicted on the charge that he rejects the liberal faith in welfare spending, higher taxes and civil liberties.

Now, there is one big difference. In May, the Massachusetts Democrats denied their endorsement to King, backing the more liberal Dukakis by a 2-to-1 margin. On Saturday, the Connecticut Republicans endorsed Weicker over Prescott Bush by almost as wide a margin.

That difference is not explainable by the difference in the states, their political structures or prevailing public moods. Nor does it mean that Weicker has offended the sensibilities of the Connecticut Republican delegates less than King has "sinned" in the eyes of Massachusetts Democrats.

The difference turned entirely on the parties' contrasting perceptions of their own political positions--and the freedom they felt to give themselves "their druthers." Because Massachusetts is, practically speaking, a one-party Democratic state, the delegatesfelt entitled to insist on a candidate like Dukakis who espoused the "true faith" of liberalism. Because Connecticut is, except for Weicker, virtually a one-party Democratic state, the Republican delegates were finally convinced that they could not safely indulge their own preference for Bush's conservatism but had to accept Weicker as the candidate who could win.

In neither case was the convention necessarily the final judgment. King and Dukakis will slug it out in the Sept. 14 Democratic primary. Bush could have taken on Weicker in the GOP primary, but yesterday decided that he would not challenge the party endorsement.

Polls have shown that both King and Weicker were running weakly among those who vote in party primaries, but it would be a mistake to discount either man. There is one final paradox in the situation.

Both men are blunt, undiplomatic, unabashed and outspoken enemies of their own parties' establishments. They go out of their way to stick their thumbs in the eyes of those who demand personal and ideological deference. And because they are burly, crude, contentious men, who, in Weicker's phrase, "hang tough" for their own truths, a lot of voters trust and support them even when they disagree with them.

The voters--or a good many of them, anyway --prefer one guy with guts over a whole party with its principles. Now, it is hard to run a government with prickly characters like King and Weicker. But it's also hard to ignore the fact that their defiance of discipline puts the parties to a needed test.

That's why it's been so worthwhile to keep coming back to Bradley Field this year..