Donald Trump has been compared to Barry Goldwater and George McGovern: Sometimes parties nominate candidates who can’t win in November. But 1964 was an unwinnable year for Republicans, and 1972 was an unwinnable year for Democrats. Nominating Trump would mean picking a relatively weak candidate in a year that appears to be winnable.
In the RealClearPolitics average of polls on March 1, 2012, President Obama was up 4.6 points on Mitt Romney. In its averages today, Marco Rubio and Ted Cruz are both beating Hillary Clinton while Trump is losing to her.