George Bush is looking to a powerful ally on Pennsylvania Avenue for help in seeing that his most valuable campaign asset, the current 65-month economic recovery, will last at least until Election Day. The ally is not President Reagan but a political supporter who occupies the building next door, Treasury Secretary James A. Baker III. And some economists contend Baker may be giving the vice president more than just advice. Treasury officials won't comment on the speculation, but some economists point to recent activity in international markets as evidence that Baker has been leaning hard on major U.S. trading partners to help elect Bush and other Republicans. These actions include recent intervention in currency markets by other central banks and heavy foreign purchases of U.S. Treasury securities, particularly by Japanese investors _ measures that can help stabilize the shaky dollar, minimize inflation and help keep the economy on an even keel. A leading proponent of such a view is David Hale, chief economist of Kemper Financial Services in Chicago. He cites the spending of huge sums by Japan and other countries to stabilize the dollar, at prices higher than investors are willing to pay, as a form of ``political insurance'' for Bush. Foreign allies ``don't want to see a big discontinuity in U.S. economic policies. It's not so much that they're against Dukakis and for Bush. They just want stability in the United States in an election year,'' Hale said in an interview. ``Two years ago, Washington wanted a lower dollar. Now Washington wants a strong dollar, at least until the election. Because Baker is fearful that a dollar decline could lead to another stock market crash,'' Hale said. Although a weak dollar can help ease the trade deficit by making U.S. goods more competitive, it can also reignite inflation and drive foreign investors away from Treasury securities and other dollar-based investments, threatening the financing of the government's huge budget deficit. Foreign-exchange reserves held by the world's central banks last year grew to $790 billion from $559 billion, and Hale estimates that two-thirds of this increase comes from efforts by central banks to support the dollar. The Bank of Japan reportedly has earmarked another $60 billion to spend this year to help prop up the dollar against the yen, after expanding its foreign-exchange holdings by $40 billion in 1987. At the same time, foreign investors have become the single largest buyer of Treasury securities. This helps underwrite the U.S. budget deficit, since selling Treasury bonds and bills is the government's primary way of financing its red ink spending. Analysts estimate that Japanese investors alone bought as much as half of last week's sale of $8.5 billion in new 30-year Treasury bonds. Analysts have speculated that the government of Japan persuaded them to do so, perhaps as a favor to Baker. If Japanese and other foreign investors were to withdraw their stake in Treasury securities, interest rates would be forced up sharply, possibly triggering a recession. An economic downturn at this point could spell disaster for Bush's presidential efforts. And while most economists don't see a recession likely in the months ahead, many forecasters are expressing new fears about an escalation in both inflation and interest rates. Bush has been wielding the recovery _ a peacetime record _ as a major campaign weapon. While he scoffed at Reagan's policies as ``voodoo economics'' in 1980, he now regularly extols them on campaign stops as the ``American miracle.'' The similarity in phrasing to the ``Massachusetts miracle'' trumpeted by Democratic front-runner Michael Dukakis is no coincidence. Bush strategists claim the vice president will launch a major assault on Dukakis' claim after the party conventions this summer, seeking to demonstrate that the job-creation claimed by Dukakis as governor is merely an outgrowth of Reagan-Bush economic policies. However, for the strategy to work, the economy must continue to perform vigorously in the months to come. Last week's report that the U.S. trade deficit shrank by $4 billion between February and March provided some needed market-driven stimulus to the ailing dollar. However stock and bond markets slumped as investors worried that rising U.S. exports without an accompanying reduction in imports could fan inflation. Baker is an early Bush supporter and is expected at some point to assume a key role in managing Bush's general election campaign. Baker said Thursday, ``For now I'm staying at the Treasury Department.'' Bush lieutenants have suggested that, at least for the time being, Baker may be more useful to Bush there. ``It may be more prudent to seek his advice as a Cabinet member'' rather than bringing him into the campaign, said Bush's staff chief Craig Fuller. Treasury officials refused to comment on allegations that Baker was using his influence to try to persuade Japanese, West German and other governments to take steps that would promote an economic environment conducive to a Bush victory. But one official, who demanded anonymity, said that trying to keep the United States out of a recession does not exactly run contrary to Baker's role as Treasury secretary _ regardless of which candidate it might help.