MIAMI, Florida — After announcing on Monday that he is running for President, Sen. Marco Rubio’s (R-FL) campaign launched an ambitious fundraising effort to capitalize on the energy from his announcement, hoping to prove his viability in what is expected to be a crowded Republican primary field.

Near the end of his speech Monday evening, Rubio urged supporters to visit his website, marcorubio.com. According to Rubio spokesman Alex Conant, 50,000 unique visitors went to the site right after Rubio mentioned it, crashing the server.

Team Rubio quickly got the site back up and running, and offered a variety of “Day One Supporter” merchandise for those who donated on the first day of his campaign, including decals, T-shirts, and autographed posters. Rubio and his campaign account, @TeamMarco, tweeted the Day One items several times.

The effort is a reflection back to the early supporters of Rubio’s 2010 Senate race, where he was viewed as an extremely unlikely longshot against then-Governor Charlie Crist (R-FL). As Rubio gained on Crist, those who had supported him from the beginning proudly began calling themselves the “Three Percent Club,” a reference to the abysmal 3 percent showing Rubio had in an early poll.

“Back in 2009, Marco started with only a handful of supporters, and won,” Conant told Breitbart News. “We start as the underdog again now, and want to give early supporters something special to show that they were with Marco from Day 1 for years to come.”

Rubio’s online fundraising efforts will be assisted by some major heavy hitters he has attracted to his campaign. As Breitbart News’ Matthew Boyle reported on Monday, Wall Street billionaire Paul Singer is backing Rubio. Singer is known for not only writing seven-figure checks to Super PACs, but also urging his wealthy friends to join him in financially supporting his chosen candidates and issues.

With Sen. Rand Paul (R-KY) raising over $1 million in the first day after his campaign launch, and Sen. Ted Cruz (R-TX) backed by a group of Super PACs that raised over $31 million in a week, a strong early showing by Rubio is critical for him to establish himself as a top contender. Political chatter has Rubio’s fellow Floridian, former Gov. Jeb Bush, taking in eye-popping numbers — rumored to be $1 million a day and headed to a $100 million war chest — further adding to the need for Rubio to establish strong momentum early on.

Follow Sarah Rumpf on Twitter @rumpfshaker.