With his nomination by the Republican Party virtually assured, Lawrence J. Hogan's chances of becoming the next U.S. senator from Maryland will depend largely on the people who frequent places such as Hen Kahler's restaurant off Rte. 695 in southeast Baltimore County.

Hen Kahler's, a popular neighborhood bar and crab house adorned with a Budweiser clock, is in the heart of Democrat country. It is blue-collar, industrial and often packed with union activists who in the past have shown unwavering support for incumbent Democratic Sen. Paul S. Sarbanes.

Despite the overwhelming odds against success in Sarbanes' strongholds here--there is an 8-to-1 registration ratio in favor of Democrats in southeast Baltimore County and 3-to-1 statewide--Hogan dutifully met with local Republican faithfuls recently over a lunch of shrimp salad and strawberry pie to plot the region's conversion to Republicanism. With a long cast of potential Republican challengers on the Sept. 14 primary ballot now reduced to a pair of perennial longshots, Hogan's strength among Democrats will be the acid test of his candidacy.

The controversial Prince George's County executive began to focus on the Democratic incumbent weeks ago, when there were still five or six Republican challengers in the race against him. In his only other statewide race, in the 1974 gubernatorial campaign, Hogan similarly chose to ignore the Republican challenger to concentrate on the Democratic incumbent, Marvin Mandel. The strategy turned into a humiliating primary loss to Louise Gore, but that chapter of his political history, he says, is part of the distant past.

Hogan's belief that he can capture votes in the city of Baltimore and its working-class suburbs is predicated on his success in Democratic Prince George's County, where he was elected to Congress three times and has served as county executive since unseating Democrat Winfield Kelly in 1978. Hogan says that his appeal to Democrats, blue-collar whites and ethnic minorities in Prince George's can be tranformed into statewide Hogan votes as well.

His first problem, however, is not winning over Democrats in Essex and Dundalk. It is with the regulars in his own party. Hogan is hardly a revered figure in Maryland Republican circles. For much of the past decade, his relations with party leaders have been sour. Some prominent Republicans don't like his aggressive style and his penchant for verbal combat. Others still regard him as a traitor to his party for his early declaration, while serving on the House Judiciary Committee in 1974, that president Richard M. Nixon should be impeached.

More recently, he alienated important potential allies, including Sen. Charles McC. Mathias and former representative Bob Bauman, for what some described as a "heavy-handed" (and unsuccessful) attempt to become chairman of the Maryland delegation to the Republican National Convention in 1980.

And last year, some Republicans openly criticized him for "pushing" (again unsuccessfully) his son Lawrence J. Hogan Jr. to run in a special election for the 5th Congressional District seat vacated by the ailing then-Rep. Gladys N. Spellman.

Hogan says charges that he engineered his son's entry in the congressional race were "a bum rap." He maintains that it was his son's decision to run and that initially he tried to dissuade him.

The state's Republican leadership made no secret of its efforts to find another Senate candidate early on: Rep. Marjorie S. Holt was the top choice, but she declined; then there was L. Bruce Laingen, the former hostage in Iran, and former senator J. Glenn Beall, who lost to Sarbanes in 1976.

Finally, V. Dallas Merrell, a Silver Spring business consultant who had pulled out of the race because he was $75,000 in debt, jumped back in hours before the filing deadline on July 6. Then, once again, he and several lesser-known contenders withdrew, giving Hogan his long-awaited clear shot at Sarbanes.

Some Republicans, such as Montgomery County state Sen. Howard A. Denis, play down the significance of internal party warfare, preferring to stress instead that Hogan has done a good job as a Republican county executive, considering that the Prince George's County Council is entirely Democratic.

"Under the most difficult circumstances he has repeatedly outmaneuvered his opposition and now he is emerging stronger than ever before," Denis said. "The criticism of him by Republicans hasn't really penetrated to the average party person or the people on the street. The people obviously respond to him."

Republicans at the national committee level, however, are concerned about the intraparty rivalries, especially in a year when they have a poll indicating that Sarbanes is the most vulnerable Democratic Senate incumbent. They have tried futilely to smooth the way between Hogan and his detractors, particularly state GOP Chairman Allan Levey.

While some Republicans say Hogan is getting the treatment he deserves, many blame Levey for letting personal differences and his own political aspirations interfere with the party's chances to elect a senator this year.

The schism could prove dear for a candidate who so far has raised and spent $212,000 (compared to Sarbanes, who has $800,000 in the coffers), and who needs $1.5 million to wage an effective campaign.

It has been eight months since Hogan, dressed in his campaign attire of pin-stripe suit and conservative tie, began a statewide tour that has now taken him 15,000 miles by car, helicopter and airplane in a feverish quest for voters. He has paid for television advertisements in Washington, Hagerstown, Baltimore and on the Eastern Shore.

But still few people outside Prince George's and Montgomery counties know who Hogan is. During refreshment stops along the campaign trail, he never fails to hand out his kelly-green brochure, shake hands and introduce himself as "a former three-term congressman and the county executive from Prince George's who is running for U.S. Senate."

Month after month, while Republican officials sorted through their prospects for 1982, Hogan moved around Maryland, spreading his name and his favorite campaign theme: that Sarbanes is "an extreme liberal" who is "farther out in left field than the Orioles' Gary Roenicke would ever dare to play."

Sarbanes, he says repeatedly, is a "do-nothing" senator whose only actions in Congress have been "giving away" the Panama Canal and behaving rudely to former secretary of state Alexander Haig during his confirmation hearings last year.

"We need a new lineup," Hogan says, using one of a series of sports metaphors that have punctuated his speeches to groups ranging from local Republican clubs to the Veterans of Foreign Wars to chambers of commerce.

The criticisms of Sarbanes, which include likening him to former president Jimmy Carter, move fluidly to denunciations of "big-spending" Democrats and praise for President Reagan's economic policies.

Hogan's rhetoric is a familiar trademark of the aggressive style (some critics call it "Napoleonic personality") that he has fashioned in his years as a politician.

"We haven't been the tough Yankee traders that we're going to have to be," he said to senior citizens in Baltimore when asked about the slumping auto industry. "We're going to have to play hard ball with some of these countries, especially Japan and Germany."

To 15 black Republicans gathered at the Soul Shack in Baltimore's Lexington Market, Hogan emphasized his efforts to improve racial harmony in Prince George's, mentioning that he appointed a black deputy police chief and that he himself lives "in a predominantly black neighborhood."

Hogan, an Irish-Catholic born in Boston who was well-known in Congress for his opposition to abortion, says he is confident of winning ethnic voters--even the Greek community that Sarbanes comes from--because of his "strong stands against communism."

"I fought to keep the Crown of St. Stephen's from going back to Hungary," said the former FBI agent, reciting a litany of cases in which he aided foreign-born constituents during his six years in Congress. "I'll get a lot of ethnic support."

Nothing has given him greater confidence in his ability to make inroads on the traditional Democratic vote than an announcement several weeks ago that the 500-member International Longshoremen's Association Local 1355 would endorse him instead of Sarbanes. "That's man bites dog," Hogan said of the endorsement. "When a union endorses me, that's news."

His optimism about attracting union support, however, transcends an important political reality: That Prince George's powerful police and employe unions, whose support was crucial to his victory four years ago, are now among his harshest critics. But those problems, he explained, are largely "personality conflicts."

And an endorsement from the National Right to Work Committee has led union leaders in Maryland to dub Hogan "labor's public enemy No. 1."

"We want to bury Larry Hogan. We want to rub his face in it," said Paul Manner, former head of the county chapter of the American Federation of State, County, and Municipal Employees.

Tom Bradley, president of the D.C.-Maryland AFL-CIO, said Hogan "has demonstrated throughout his political life that he is antiworker and antilabor."

When the subject of his problems with unions comes up at places such as Hen Kahler's, Hogan repeats that it is more personality than policy that is at issue. He then goes on to stress his differences with Reagan--on dredging the Baltimore harbor, layoffs of federal employes and the need to uncover waste in defense programs.

"I've gotten along with all the unions except the FOP and AFSCME," he says. "I get along real well with the firefighters, the nurses, the oilers and boilers, the house physicians and the longshoremen."

As county executive, he said he has signed 18 union contracts. "You never hear about those," he says, disgruntled. "But there are a lot of reasons that unions should endorse me. I've gotten awards from all those people."

Hogan measures his success at every opportunity. From the longshoremen's endorsement to an agreement by former congressman (and "genuine war hero") Gen. James Devereux to serve as his Baltimore County campaign chairman, Hogan is quick to point to signs of progress in his campaign. An announcement that the national Republican senatorial campaign committee was ready to help him was dispatched instantly to the press. It was a sign, his aides said, that his candidacy has national importance.

At a posh Republican rally in Cockeysville, Hogan motioned a reporter toward a handful of Democrats from the Essex and Dundalk areas who turned up wearing Hogan for Senate buttons (and ones for Democratic state. Sen. Harry J. Mcguirk, who is challenging Gov. Harry Hughes in the primary).

Several of the Democratic guests, Hogan recounted later, promised to deliver "at least 125 votes" for Hogan from fellow union men.

"There aren't too many successful Republicans in Maryland," Hogan said. "And I'm one of them."