It is not exactly a first, and in a voting context. Here is Cardinal Burke, an American bishop in Rome, in an interview with me here in 2009:

If a Catholic knowingly and deliberately votes for a person who is in favor of the most grievous violations of the natural moral law, then he has formally cooperated in a grave evil and must confess his serious sin. Since President Obama clearly announced, during the election campaign, his anti-life and anti-family agenda, a Catholic who knew his agenda regarding, for example, procured abortion, embryonic-stem-cell research, and same-sex marriage, could not have voted for him with a clear conscience.