AJIJIC, Mexico — Super Tuesday's presidential primaries will be held in 24 states — and a lot of countries. Democrats Abroad, the overseas branch of the Democratic Party, will hold its first "global primary" from Tuesday through Feb. 12, allowing party members to cast primary ballots at polling stations in more than 30 nations. Democrats overseas can also cast primary votes for the first time via the Internet, meaning registered Democrats anywhere in the world can participate. One of seven polling stations to be set up in Mexico will be in this lakeside town of bougainvillea-lined cobblestone streets, art shops,...