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Elliott Gould doesn't think Sen. Al Franken's career deserves to be sunk by Leeann Tweeden revealing he groped her in 2006 ... because that mistake doesn't define his friend.

The actor's been tight with Franken long before his political days-- Franken was an 'SNL' writer back when Elliott hosted. Despite the allegations -- many of which Franken admitted and apologized for -- Elliott stood by his friend Thursday night outside Craig's.