Richard Uihlein, a top G.O.P. megadonor, gave another $10 million in August.

Richard Uihlein, a conservative packaging supplies magnate, plunged another $10 million into the 2020 election in August, donating to the Club for Growth just as the group began spending on the presidential campaign.

The Club for Growth, a conservative political group, has spent more than $10 million since Mr. Uihlein’s donation in August on independent expenditures opposing Joseph R. Biden Jr., the Democratic nominee, and supporting President Trump.

The group announced two television ads last month, buying airtime in the pivotal states of Arizona, Pennsylvania and Wisconsin.

In addition to Mr. Uihlein, the Club for Growth received another $10 million from Jeff Yass, the founder of a Pennsylvania-based investment company, and $1 million from Richard Gaby, whose wife, Barbara Van Andel-Gaby, serves as chair of the board of trustees of the Heritage Foundation.