Overshadowed by the gubernatorial primaries in both parties, a contest for the Republican nomination against Sen. John F. Kerry (D-Mass.) has depleted the bank accounts and tested the patience of two businessmen who are new to politics. Jim Rappaport, 34, the wealthier and more conservative of the duo, is favored to defeat Dan Daly, 46, in Tuesday's primary.

Daly, who built a successful personnel agency business, has contributed at least two-thirds of the cost of his $650,000 primary campaign. Rappaport, whose father is one of Boston's most successful real estate developers, has put almost three times that much into his drive for the nomination.

Daly won the state GOP convention endorsement, but he believes that has meant little against Rappaport's money. He said that Rappaport in effect has bought the election. Polls show Rappaport positioned for an easy primary victory.

Kerry's prospective challenger has identified himself with the taxpayer revolt spawned by the spending policies and emergency revenue measures of the administration of Gov. Michael S. Dukakis (D). Unlike Daly and Kerry, Rappaport has endorsed a tax-rollback initiative that will be on the November ballot. And he misses no opportunity to remind voters that Kerry was Dukakis's running mate in 1982 and served as Dukakis's lieutenant governor for two years before his election to the Senate in 1984.

Kerry is viewed as a strong favorite, but Rappaport carries around a memo from his pollster, V. Lance Tarrance, claiming that "Kerry is among the most vulnerable Democrats up for reelection in November," in large part because the commonwealth's economic and fiscal problems have produced "the most anti-incumbent environment that any senator in the country will face in 1990."

Kerry is far from dismissing the threat. He has been campaigning hard and raising money to match Rappaport's expected spending.