KINGSLAND, Georgia— Andy Marsh tried for 14 years to make a profit running Plug Power Inc. Last summer he went to Washington and came away with a potential windfall. While senators battled over the climate, tax and spending bill, there was surprising agreement that hydrogen, Plug Power’s business, needed a big dose of support. “My biggest concern that I have right now is that we have not invested the money that we needed to invest in hydrogen,” West Virginia Sen. Joe Manchin said at a hearing in July when he was blocking the overall package.

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