PHILADELPHIA -- During the 10 years Bobby Hurst was an undercover decoy for the Philadelphia police department, he didn't keep track of the number of armed robbers he killed. "There were a few of them neutralized," he recalled.

Hurst, now campaign manager for state Sen. Joe Rocks (R), has been struggling for five months to "neutralize" just one person: Democratic challenger Allyson Schwartz.

Armed not with a gun but with an unprecedented budget of $750,000 and the all-out backing of the Republican National Committee and the Pennsylvania GOP, Hurst is in the center of one of about 40 political street fights taking place in areas as diverse as the gritty neighborhoods of West Philadelphia, the upscale waterfront homes of Palm Beach, Fla., and farms on the far reaches of Michigan's Upper Peninsula.

The outcomes of these largely unnoticed battles for state Senate and House seats across the country will be critical in determining the national strength of the Democratic and Republican parties for the next decade.

These contests stand in stark contrast to the California battle of the television airwaves between Democrat Dianne Feinstein and Republican Sen. Pete Wilson, the Texas mudslinging between Democrat Ann Richards and GOP nominee Clayton Williams, and the gubernatorial contests in Florida, Illinois, Ohio and Michigan. Each of these races has captured the attention of the news media and a significant portion of the public.

The winners of the gubernatorial contests will sign or veto the congressional redistricting plans that will be put in place before the 1992 elections. Those plans, in turn, will help determine whether the GOP remains a minority in the House or whether Republicans can begin to achieve their dream of translating repeated presidential election victories into gains in the House and in the Democratic-dominated legislatures in most states.

But the governors are only part of the political power equation that will shape the redistricting plans. The plans are written and voted on by state representatives and senators, jobs that will be filled by men and women like Rocks and Schwartz.

Millions of dollars are flowing into contests like the one here to determine whether Democratic or Republican legislative majorities will hold the balance of power in the key states. These include the state Senates in Florida (23 Democrats, 17 Republicans), New York (27 Democrats, 34 Republicans), Michigan (18 Democrats, 20 Republicans), Arizona (13 Democrats, 17 Republicans) and Illinois (31 Democrats, 28 Republicans). They also include the House in Oregon (32 Democrats, 28 Republicans), both chambers here in Pennsylvania, where the Senate is Republican by 27 to 23 Democrats and the House is Democratic by 103 to 99 Republicans, and both in Indiana, where Republicans control the Senate by 26 to 24 seats and the House by 51 to 49 seats.

With the partisan stakes driven to a 10-year high by prospect of post-1990 census redistricting, the tactics in these races are not friendly. Here in Philadelphia, Rocks, who has switched political parties twice, is struggling to survive in a district that he won as a Democrat but now must hold as a Republican.

In a city where white voter sentiments toward the faltering administration of Mayor W. Wilson Goode (D) -- Philadelphia is on the edge of bankruptcy -- are reaching venomous levels, Rocks is pulling out all the stops to discredit Schwartz.

A Rocks mailing to white voters includes two separate but adjoining photographs in which Goode, who is black, looks lighter skinned than Schwartz, who is a fair-skinned white woman.

"For the last few years, Allyson Young-Schwartz has been on a little vacation," the mailing declares. "She came from New York for a short visit, but decided to stay when she realized she could make money on the backs of the taxpayers. Allyson really liked the idea of taxpayer funded abortions. So, instead of going out and getting a real job, she decided to open an abortion clinic and worked to make you pay for the abortions."

Nearly 1,000 miles to the South, Republican state Senate challenger Bill Smith, a Boca Raton, Fla., city councilman, is conducting almost as tough a campaign to oust state Sen. Eleanor Weinstock (D). A Smith television ad shows the candidate wearing a green sheriff's T-shirt during a drug raid.

"The comparisons are stark," the ad says. "On the number one issue in Palm Beach and Broward counties, crime and drugs, state Senate candidate Bill Smith has a clear position. He is for the death penalty. His opponent, incumbent Eleanor Weinstock, voted against a bill which became law that applies the death penalty to big-time cocaine dealers. Your vote counts. Vote for getting tough on lawbreakers."

Neither Weinstock in Palm Beach nor Schwartz in Northwest Philadelphia has been timid about fighting back.

Weinstock, a determined liberal in a district moving rapidly toward Republican ascendance, has countered with a commercial declaring: "Weinstock supports life imprisonment without the possibility of parole. Eleanor Weinstock supports mandatory sentences for selling drugs. She supports banning military-style assault wepons."

Schwartz and the Pennsylvania Democratic Party have counterpunched Rocks's assaults with mailings using a photograph of Rocks in which he looks like a dead ringer for the "What-Me-Worry" figure in Mad magazine to portray him as both a party switcher and a switcher on issues important to labor, teachers and other interest groups that remain strong here.

Going into the final week of these battles, strategists for both parties suggest that the trends are favoring the Democrats. Republicans have a shot at taking the Florida Senate, probably giving them a secure base in the state through the 1990s.

But Democrats have shots at winning the state Senates of Michigan, Pennsylvania and Arizona, with New York a longer shot for a Democratic takeover. Democrats could loose the Oregon House to the GOP, but the Democrats stand a chance of picking up both branches in Indiana.