In Maryland's long and tumultuous political history, there has never been a legislative session like the one that begins Wednesday, and there won't be another one until 2002.

This is the first time that an election year has coincided with a year of reapportionment, placing Gov. Harry Hughes and the 188 members of the General Assembly in unprecedented political peril. Their every vote and gesture will be watched closely by hopeful opponents or constituents back home, even as legislators fight on the floor to keep their old power bases from being shifted to new districts and Hughes seeks to steer his proposals through the crossfire.

Against this backdrop, politicians appear hungry for a year of easy issues --the sort that touch few voters, stir little controversy and generate lots of good publicity back in the home district. But 1982 is not one of those years. Instead, the legislature's agenda is jammed with bills that could gouge or soothe almost every constituency in the state.

These include measures that would boost the tax on gasoline in Maryland, raise interest rate ceilings on consumer loans and retail credit, toughen gun control, increase the legal drinking age from 18 to 21, place a new prison in Western Maryland, liberalize divorce laws, increase welfare benefits and raise the pay of legislators and the governor.

The legislature also must vote to enact far-reaching changes in the state budget -- changes prompted by the Reagan administration's federal aid cutbacks -- that will eliminate or reduce basic services to thousands of Marylanders.

"From the standpoint of elected officials, there are an unfortunate number of substantive issues this year," observed a top General Assembly staffer, tongue-in-cheek. "Where is child pornography when we need it?"

The stakes are perhaps highest of all for Hughes, the one-time outsider elected in 1978 on an integrity-in-government platform, who last year suffered a loss of popularity in several statewide polls. While several of his predecessors were accused of abusing power, Hughes has drawn criticism for not using it enough. Legislators and activists in his own Democratic party complain that he has created a leadership vacuum. Recently the complaints have spread to business and consumer groups. Hughes' aides say the image is undeserved, but acknowledge that he must reverse it in the 1982 session.

"What's at stake for Harry Hughes in this session is the immediately lasting public impression of his first term," Lou Panos, Hughes' press secretary, said last week as the governor completed a Caribbean vacation to rest up for the make-or-break session.

In recent weeks, the traditionally reserved Hughes has taken decisive stands on some of the major issues, notably a proposed gasoline tax increase to rescue the state's strapped road and bridge fund and an ambitious anti-crime package that includes a strong gun control bill. Support Weakened

While the moves won praise from some critics, they also tied Hughes' reputation as a leader to the fate of several volatile measures. Because of his strained relationship with many legislators, this strategy is expected to have mixed results, even in an election year when a lopsidedly Democratic General Assembly would be expected to rally around a Democratic governor.

"I personally don't want to do anything for the governor," said Del. Timothy Maloney (D-Prince George's), one of Hughes' most vocal critics. "We might be willing to vote for a gas tax in an election year if we do it for the people of Maryland, but if it's let's-do-it-for-Harry, forget it."

"If the frustration level gets much higher, someone will run against him in the primary ," said a leading Democrat who declined to be identified. "He has a battle ahead of him and he's got to recognize it."

The most obvious test of Hughes' leadership is his proposal to raise the state gasoline tax by a formula that would probably add about four cents a gallon to the pump price of gas, a distasteful prospect for legislators in an election year. A similar Hughes proposal died last year on the final night of the session. This year, many legislators say they might be forced to support it because Maryland's transportation finances are so depleted, with roads and bridges falling into dangerous disrepair.

"I am personally convinced we should pass the gas tax this year," said House Speaker Benjamin L. Cardin (D-Baltimore), whose support is considered essential. "It's the responsible thing to do."

Even so, the legislature is sharply divided over how the new tax money should be used, with rural and outer suburban contingents insisting that the tax money go to their roads and bridges, and the powerful urban delegations from Baltimore and the Washington area concerned about mass transit aid. Unless each side makes major concessions, Cardin said, the gas tax is doomed. And bumpy roads could become a political issue against any incumbent.

The one issue on which Hughes and most legislators are solidly united is the battle against crime, the 1982 bandwagon issue that has generated piles of legislation from all areas of the state. A recent statewide poll showed Maryland's sharply rising murder and robbery rates to be the No. 1 concern of voters, ahead of inflation and unemployment.

Hughes' crime package, backed by legislative leaders, includes a gun control measure that would impose a mandatory one-year sentence on anyone caught carrying a handgun without a permit -- a proposal that has drawn fire from the gun lobby. Stiffer Sentencing

Other bills in the package, considered less controversial but more significant, would impose mandatory sentences for some major drug offenses and force repeat juvenile offenders to face trial as adults for certain serious crimes. In addition, Hughes and legislative leaders are supporting construction of a new, medium-security prison in Hagerstown, despite loud resistance from voters and politicians there.

Hughes' stance on crime is being monitored closely by his most likely Republican challenger, Anne Arundel County Executive Robert Pascal, who has a box seat on the legislative session from the county office building down the street from the statehouse. Pascal has attacked Hughes for more than two years as "soft" on crime, and now accuses the governor of political expediency in seizing the anti-crime momentum.

That momentum is expected to spill over into a separate campaign to crack down even further on Maryland's drunken drivers, who already face some of the stiffest state laws in the nation. As a result, the legislature is considered likely to raise the legal drinking age to 21 -- a measure that died last year in a House-Senate feud -- billing the move as an effort to curb traffic deaths related to teen-age drinkers.

With such a groundswell of support for a crackdown on crime, some legislators say their only fear is that the General Assembly may go too far, particularly in setting mandatory sentences that could pack the state's already overcrowded prison system.

"We've got to make sure the cure is not worse than the disease," observed House Judiciary Committee Chairman Joseph Owens (D-Montgomery).

Although it has generated less furor than the crime issue, Reaganomics and its impact on the budget are considered by many the most important issues of the session. "In my mind, it is the issue," said House Majority Leader Donald Robertson (D-Montgomery). "I'm concerned that some of these reapportionment and reelection fights will absorb a lot of time and attention that need to be focused on the budget."

One striking symbol of the chaos that Reaganomics has brought to Maryland will be unveiled on the first day of the session when, according to sources, more than 200 employes in the state's Employment Security Administration are to receive layoff notices because of the most recent round of budget cuts.

"We thought the cuts were over for awhile, and suddenly we realized that we lost $5 million" in the continuing resolution passed by Congress last month, an administration official said. The layoffs will reduce counseling services to the unemployed dramatically, officials said.

The budget battle will be another test of Hughes' leadership. Aside from substantial losses in federal aid, the state's economy has performed better than expected, creating a modest surplus with which the governor has said he hopes to "blunt the cruelest" of the Reagan cuts.

He already has endorsed a regulatory change that would restore to the state's welfare rolls 3,000 working, poor families who otherwise would have lost all benefits. And his budget includes 9 percent increases for the state's welfare recipients and for the strapped foster-care system. Still, some 20,000 Marylanders will be cut from the welfare rolls, and many more will lose services.

"Politically, some people are concerned that the responsibility for the full impact of any cut, anywhere, in any program, will end up on the wrong desk," said a Hughes administration official. "That is, on the governor's desk, instead of on the president's or on Congress's."

The Hughes budget is expected to get caught in election year politics as legislative committees scrutinize it to see if it passes the test of fiscal conservatism. "The governor's budget will be looked at v-e-r-r-r-ry closely," promised House Approriations Committee Chairman John R. Hargreaves, a conservative from the Eastern Shore who questions some expenditures for social services.

However, politics could cut both ways on the budget battle. A senior state budget adviser noted that voters in Maryland, which has a strong liberal constituency, may be "sick of budget cuts," and supportive of Hughes' tone of humanity amid austerity. Then again, they may have been converted to Reaganism. Power Struggle

And the battle could become even more complicated because of redistricting. Several legislators have noted that Hargreaves stands to lose much of his power base, and could hold the budget hostage to get concessions. The cagey Hargreaves scoffed at the prospect last week.

"This chairman has been accused hundreds of times of doing that," he said. "That doesn't mean he did. That doesn't mean he wouldn't."

As Hargreaves spoke, Hughes' aides were up on the second floor of the statehouse, studying major legislative packages on which he has yet to take a position: interest rate deregulation, divorce law liberalization, drunk-driving laws and more.

Meanwhile, press secretary Panos was at work on Hughes' State of the State address, to set the tone for his legislative program. Last year, Hughes' speech was not interrupted by applause. Many politicians speculate a "new Harry Hughes" will emerge with a rousing State of the State speech this year.

Panos is keeping the tone of the speech a surprise, promising only, "It will be very statesmanlike." Asked if it will be rousing, he answered: "Harry Hughes is not a rousing kind of guy. You can't phoney him up.''