Despite those big smiles and heartfelt handshakes, life isn't always smooth for the candidates on the campaign trail. All the event planning and preparation can quickly fall apart when a vocal demonstrator tries to rattle a candidate with their message.

For the media, these spontaneous moments can make an instant headline; for the candidate, it can be a make-or-break moment that shows how they react in knee-jerk situations. And for the 2012 race, there has been no shortage of cringe-worthy headlines.

Many of the awkward moments have come from the mouths of demonstrators trying to rattle the candidate. Because much of the campaign trail is mapped along public events, supporters for rival campaigns or even rival parties can show up for a little audience participation.

Such was the case for GOP candidate Newt Gingrich in Iowa. Just as he was about to take to the podium, a group started chanting, "Put People First," forcing him to delay his opening remarks. The group was removed and he eventually made his speech, but it wasn't exactly according to plan.

Fellow GOP candidate Mitt Romney was also interrupted in the Hawkeye state, during the Iowa State Fair. Romney was trying to make a speech for a group of supporters when someone in the crowd started shouting questions about his views on Social Security, Medicare and taxes. Instead of ignoring the interruption, Romney attempted to stop the questioning with a line that eventually went viral; 'Corporations are people, my friend.'

Even President Obama has had his share of encounters with protesters during speeches. In late November, he made a stop in Manchester, N.H., where a vocal group attempted to outmatch the president's speech on jobs and the extension on the payroll-tax cut. The president let the protesters have a few minutes on the floor, but thery were eventually overtaken by the supporting crowds, chanting Obama's name.

And it's not just vocal crowds that can shake a campaign. Republican candidate Michele Bachmann was caught off guard during a book signing stop in South Carolina by an 8-year-old with a message about his mother. The exchange was caught on tape, as Bachmann strained to hear the boy say, "My mom is gay and she doesn't need fixing."

But perhaps one of the most colorful interruptions so far on the campaign trail was a demonstrator's attempt to visually show Newt Gingrich his message about gay rights. As Gingrich was signing books, the demonstrator dumped a box of glitter over the candidates head, telling Gingrich to, "Feel the rainbow, Newt."

While they might not define a campaign or permanently change a candidate's image, the unscripted and unrehearsed responses can offer voters a chance to see something they might not otherwise get from a stump speech. How a person reacts to conflict and confrontation on the trail could very well indicate how they would handle themselves inside the Oval Office.

So, while it might be uncomfortable for them, it could be an invaluable snapshot for voters in determining who is best to lead the country.