CHICAGO — Each of the four remaining contenders for the Republican presidential nomination has sparkled at one point or another during the campaign. We’re talking, of course, about “glitter bombing.”

That is the protesters’ tactic of flinging glitter at candidates and other political figures who oppose their cause, often same-sex marriage.

Nick Espinosa, a gay rights activist and a member of both the protest group Occupy Minneapolis and another called the Glitterati, is credited with launching the glitter-bombing phenomenon last spring with a sparkle strike at presidential candidate and former U.S. House Speaker Newt Gingrich during a book signing in Minneapolis.

“What I have tried to do with creative forms of protest like glittering is to capture people’s imagination and tap into a cultural point of reference with a piece of political theater,” Espinosa wrote in a piece last fall for The Huffington Post, in which he boasted of the glitter attack on Gingrich.

“The strength of glitter is that humor is an incredibly powerful tool for communicating a message — even a deadly serious one.”

The glitter bombings, labeled assaults by some, have led to arrests in some cases and seem to have become more common of late:

Rick Santorum was glitter-bombed by a protester in Blaine, Minn., on Tuesday, the same day he swept caucuses and a primary in three states. This was at least the fourth glittery encounter for Santorum, following similar events last month in South Carolina and Florida, and Friday in Missouri.

Mitt Romney, the presumed GOP front-runner defeated by Santorum in Minnesota, Colorado and Missouri, was nearly glittered Tuesday night at an event in Denver, but the tiny projectiles fell short. Romney wasn’t so lucky Feb. 1, though, when glitter was fired at him as he took the stage at a campaign event in Eagan, Minn. Quick on his feet, Romney declared it “confetti,” thrown in celebration of his win a day earlier in the Florida primary. On Twitter, Espinosa took credit as the “glitterer.”

Fellow Republican presidential hopeful and U.S. Rep. Ron Paul was showered by the glimmering bits on Monday, not by Espinosa or by a glitter-bomber calling for gay rights, but rather by a protester demanding equal access to housing and health care.

Among the other reported glitter victims: former GOP presidential candidates Tim Pawlenty (a former Minnesota governor) and Michele Bachmann (a U.S. representative from Minnesota); U.S. Rep Erik Paulsen, R-Minn.; Republican political consultant Karl Rove; and members of Minnesota for Marriage, a group opposed to same-sex marriage.

But glitter bombing is not strictly a tactic used against Republicans. Little-known presidential candidate Randall Terry, an anti-abortion advocate running as a Democrat, was glittered at a candidates forum in New Hampshire in December … by fellow fringe Democratic candidate Vermin Supreme, a performance artist.