Sarah Begley wrote about the role that late night talk shows play in helping candidates run for President:

• Talk shows can help redeem a candidate in trouble. In 1988, after a speech by Bill Clinton fell flat, he appeared on the The Tonight Show Starring Johnny Carson with a saxophone. It rehabilitated his image and made people forget about the speech.
• Talk shows can be a barometer of the political mood. In 2008 Obama was the target of jokes when his poll numbers were down. Then McCain called the economy fundamentally sound during a period of crisis. The comedians had a new target to aim jokes at the polls swung.
• If a candidate doesn’t have a narrative around them, then talk show hosts will create one with their jokes. It’s better then to show up at a talk show and help guide the narrative.

Read more here.

Source: Time