It's one of the basic rules of good writing: Don't mix your metaphors. As reported by the New Republic's Jonathan Chait, Eric Alterman of the Daily Beast provides an illustration of why the rule is so important and why ignoring it can make things go very, very wrong. The passage in question is truly a gift to English teachers everywhere in their quest to convince students to avoid clichés.

And yet even with all its proverbial ducks lined up—a populist crusade is just what the doctor ordered for a divided and dispirited party going into perilous midterm elections—the administration and its lieutenants in Congress are still shooting as many blanks as real bullets at the bad guys. It’s not that their bills are all bullshit, as the Republicans’ clearly are. They contain many worthy measures that would, as almost any fair-minded economist will tell you, provide a proverbial “step [or two] in the right direction.” But somewhere along the line, whether in Obama’s White House, Tim Geithner’s Treasury Department, Barney Frank’s House Banking Committee or Christopher Dodd’s Senate side, a decision was made to let the big fish get away.
What is he even saying? Who knows! Other writers have taken the opportunity to poke fun at Alterman's prose. Chait calls this "Like Teaching An Old Dog That Didn't Bark To Herd Cats." The Huffington Post's Nico Pitney quips, "Finding all the cliches and mixed metaphors in this Eric Alterman paragraph is like cutting fish in a barrel with a butter knife."