This cartoon by John Cole, editorial cartoonist for The Times-Tribune is part of a collection of cartoons from The Cagle Post relating to President Obama's support for gay marriage. The Guardian explains the context:
Obama's announcement, in a hastily-arranged ABC interview on Wednesday, came after years of dodging the issue. He was forced to go public partly because vice-president Joe Biden ignited the debate with a remark in support of gay marriage at the weekend.
In the interview, Obama said he had long supported civil unions but his position on same-sex marriages had been evolving because of the powerful traditions and religious beliefs attached to the word marriage.
1. A shotgun wedding is a wedding that has to take place quickly, often because the woman is pregnant. The cartoon implies that Obama was forced to come out in favour of gay marriage because of Biden's remarks, which is why Biden is portrayed with a shotgun for a mouth. The cartoonist may also have been thinking of the expression to shoot one's mouth off, which means "to talk too much in a loud and uncontrolled way".
2. If you are uncertain about the difference between the words 'marriage' and 'wedding', a good rule of thumb is that marriage refers to the institution and wedding to the ceremony.
• The wedding cost over $25,000 but their marriage lasted just a few months.
• Biden pushes Obama to declare gay marriage support, then offers his apologies (Chicago Tribune)