Jonathan Chait demolishes this latest meme from the right. His main points:

"1. Al Gore did not challenge the validity of the election process.

2. Respecting democratic outcomes does not, contrary to Scarborough, mean insisting that an election has never been rigged.

3. It is not only legitimate but factually true to point out that the 2000 Florida recount failed to produce an outcome that matched the discernible preferences of the plurality of the voters.

4. The conservative line relies on lumping together Gore, who followed the process and conceded afterward, with his supporters, many of whom disputed the fairness of the process afterward.

5. Trump’s dispute of the election’s fairness is embedded in a party-wide hallucination about systemic voter fraud. 

6. Trump is delegitimizing the election on the basis of evidence-free conspiracy theories."

http://nymag.com/daily/intelligencer/2016/10/donald-trump-is-not-like-al-gore.html