This gritty, blue-collar suburb of Milwaukee has always been a Democratic stronghold. "This is a union town," druggist Clifford Schybowski tells a visitor. "They hate Republicans here."

Under these circumstances, an incumbent Democratic president shouldn't have political trouble in a place like this. But there is a strange undercurrent of unrest running through this ethnic community.

"People are pretty frustrated. There's a lot of disenchantment with Jimmy Carter," says West Allis Alderman John Turck. "I was surprised the New York thing didn't happen sooner."

Strangely enough, the chief beneficiary of the unrest in Wisconsin's presidential primary Tuesday may not be Sen. Edward M. Kennedy, who upset President Carter in last week's New York primary, or even California Gov. Edmund G. Brown Jr.

The beneficiary may be, random interviews indicate, Ronald Reagan, the conservative Republican.

"Normally, I vote Democratic," says Gilbert Leack, a retired railroad worker. "But you know there's only one way to vote this time, that's for Reagan. This guy Carter just doesn't fill the bill."

Leack and many of his neighbors are angry about the Iranian hostage situation. "This Iran thing is just a big political deal," he declares. "I think we've been too pussyfoot. We're a big country. And we aren't handling ourselves like a big country."

Others are restless over the economy. "I really get frustrated when I see my parents going from lower middle class to upper lower class and taking most of this town with them," says Greg Gaffke, a student at nearby Carroll College.

Reagan's support among conservative, blue-collar Democrats has been one of the most underreported phenomena of the 1980 presidential race. But Democrats who crossed party lines and voted for the former California governor had a profound impact on the Illinois GOP primary and they may have a similar impact on the results of Tuesday's GOP primary here.

It has happened before in Wisconsin, and no other state makes crossover voting quite so simple. Regardless of their party affiliation, voters are given a choice of voting in either the Republican or Democratic primary. Whichever they choose has no effect on races for local offices, all of which are nonpartisan.

Reagan and Rep. John B. Anderson (R-Ill.) have made blatant efforts to court Democratic voters. Most of the attention, however, has focused on Anderson, who has gone after the support of students and liberal Democrats, dropping hints that he may ultimately run as a third-party candidate if he fails to win the GOP nomination.

The Reagan crossover comes from the opposite side of the political spectrum. Surveys indicate it is related to his stands on a series of gut social issues -- abortion, gun control, welfare and national defense.

In part, his support in places like West Allis, home of a large Allis-Chalmers plant, is the same that George Wallace received in the 1972 and 1976 Democratic primaries. "Reagan is my man," says Eddie Pausch, a middle-aged industrial worker and former Wallace supporter. "He'll abolish welfare if he gets in."

But the appeal runs deeper in West-Allis' highly Catholic neighborhoods, with their large populations of Poles, Serbians, Slavs and Italians.

"Reagan has the same image as these people have of themselves," says his Milwaukee county coordinator, Louis Collison. "He stands for the home and the family. He's against abortion. He's against waste. These are religious people who work hard and believe in saving money. They are one of the last bastions of society that still believe a wife should stay at home."

Anderson appeals to some of their same populist, anti-establishment instincts. "I like what he's saying and he's honest," June Grudichax, 62, said as she left Van's Supermarket yesterday. "But he doesn't have a chance to get elected.And I'm not going to throw my vote away."

Until recent weeks, many of those interviewed said they intended to vote for President Carter. Iran, however, tipped the balance against the president. "Carter is an honest man," Robert Lee, a steelworker, said outside his white bungalow. "But he didn't do anything about those hostages. He should have gotten them out a long time ago."

Wisconsin has a tradition of independent voting that dates back to the early 1900s when Gov. Robert La Follette set up an open primary system in an attempt to break the control the big railroad and timber companies held over state politics.

In recent primaries, crossovers into the Democratic party have created the most controversy. In 1968, political scientist Austin Ranney found that one-fourth of the Republican voters cast their ballots in the Democratic presidential primary. Of them, 20 percent voted for antiwar candidate Eugene McCarthy. In 1972, Republican crossovers accounted for 20 percent of the vote in the Democratic primary. Former Alabama governor Wallace got half of them.

As part of a reform effort, the national Democratic Party attempted to do away with crossover balloting in the state this year. But the Wisconsin Supreme Court overruled the move.

Reagan is so confident that he will win the GOP primary here that he campaigned only two days in the state last week. He will also be here Monday.

Seventy-five Democratic delegates and 34 Republican delegates are at stake in Tuesday's voting.

While in the state, the former California governor made his most pointed attempts of the year to attract Democrats. "At the conservative end of the Democratic spectrum people are more and more going to vote Republican. . . . I intend to make my appeal across-the-board to Democrats and independents," he said at an outdoor rally in Waupaca.

Symbolically, he scheduled his only major appearance in Milwaukee at Serb Memorial Hall, traditionally the Democratic Party's temple on the city's south side.

He was the first Republican presidential candidate ever to appear at the hall, located less than a mile from West Allis. And he drew an overflow crowd of more than 1,000.