Given Lieberman's conduct and contributions to the campaign, its not an exageration to say that choosing a block of wood as a running mate would be a better choice.
Lieberman as a campaigner was a complete disaster from start to finish. Simply by insisting on running both as VP and for the Senate, he expressly demonstrated a nationally visible lack of faith in Gore's campaign, while transparently hedging his bets. Gore's acceptance of this made him seem weak and vacillating. Lieberman seemed to revel in attacking Democratic constituencies, yet had no traction at all on the right wing. In particular, his 'culture war' attempted campaign effort against moral decay in Hollywood fell flat with an embarrassing thud. He alienated Democrats, without neutralizing or enlisting undecideds or right wingers. I don't think he did much in any significant way to attract or maintain jewish support, which was predominantly Democrat in any event. Outside of his own senate constituency, he had no particular following or broadbased constituency, spoke to no one about anything. So the question is clearly, who was he supposed to appeal to. His performance in the debates with Dick Cheney was spectacularly cringeworthy, at times he seemed to simper. His selection was a vicious and overt slap in the face to Clinton supporters and seemed calculated to repudiate that support. He was probably one of Nader's biggest recruiters by default. In the controversies that followed the election, Lieberman repeatedly sabotaged the Gore position, and seemed perpetually willing to surrender.
It's really difficult to imagine Gore doing worse than Lieberman. Almost any pick would have been dramatically better.
At times, it seemed Gore was working hard to lose the election, and certainly the media never withheld their contempt for him. But Lieberman was the nadir.