Vice President Bush, trying to ensure a Republican victory in traditionally Democratic Maryland, stumped today for GOP congressional candidate Helen Delich Bentley in a district where heavy Republican voting could guarantee a statewide victory for President Reagan in Tuesday's election.

Bush's visit to Baltimore County, an affluent district and the state's bedrock of Republicanism, followed separate appearances in Baltimore last week by Walter F. Mondale and his running mate, Geraldine A. Ferraro.

An enthusiastic crowd of 1,000 supporters waving American flags and singing the National Anthem packed the National Guard Armory here and cheered as Bush hailed the nation's economic recovery and branded Mondale's pledge to raise taxes "one of the all-time bloopers in the history of American politics."

But while he and his economic message struck a responsive chord with the affluent Republicans here, Bush encountered the heaviest heckling of his campaign when he traveled later today to New Castle, Pa.

A crowd of about 200 people, evenly divided between Reagan-Bush partisans and Mondale-Ferraro supporters, tried to drown each other out with chants of "four more years" and "three more days," as Bush preached the Reagan gospel of peace through strength and economic recovery.

The Reagan-Bush campaign made a last-minute decision to send the vice president to Pennsylvania, one of four states where Mondale has come within striking distance in polls taken during the past week.

New Castle, in the heart of the depressed steel towns of the Mahoning Valley, has an unemployment rate of 22 percent, three times the national average.

"Some have not yet fully participated in this recovery, but it is essential that we keep it going, that we not go back to the malaise and despair days of Jimmy Carter and Walter Mondale," he said, as hecklers roared back, "We want Fritz."

"Some don't understand it," Bush said.

Although most of Bush's appearances have been in affluent areas such as Baltimore County, aides said he deliberately campaigned in New Castle to try to demonstrate that the Reagan-Bush ticket has a message for unemployed Americans as well as those who have prospered under Reagan.

He chose as his site a warehouse scheduled to be converted into a steel mill with the help of an $800,000 federal grant.

"Our sleeves are rolled up and we are working with you for a better future," Bush said, trying to ignore the constant heckling that dogged his entire 10-minute speech.

Bush's earlier appearance in Baltimore County was his 17th on behalf of GOP congressional candidates, and he used today's visit to lavish praise on Bentley, who is in a close contest against 11-term Democratic Rep. Clarence D. Long in Maryland's 2nd Congressional District.

"I've known Helen a long time, and I'll tell you, I wouldn't want to have to debate her," Bush said. "Geraldine Ferraro is a pushover compared to this woman."

His appearance was also aimed at spurring voter turnout in the county, an area of increasing importance in state elections. Growing in population and conservative spirit, Baltimore County now has the potential of producing enough GOP votes to offset the Democrats' strongest base of support in the state, Baltimore city, officials of both parties say.