After receiving a major boost to his 2016 presidential bid from influential hedge fund billionaire Paul Singer, Marco Rubio scored another big endorsement from Republican Sen. Cory Gardner on Monday.

Gardner, a rising star in the Republican Party, became the first senator to announce his support for Rubio's bid in the 2016 race.

"Today I am proud to announce my endorsement of Marco Rubio to be the president of the United States," Gardner said on Fox News, according to Politico. "Our country needs a new generation of leadership and I believe Marco Rubio presents this nation with the greatest possibilities and opportunities to meet the challenges of this generation."

The support from the Colorado senator comes just days after Singer, a wealthy Republican fundraiser and donor, endorsed Rubio's 2016 campaign, reports CNBC.

Unlike the majority of the conservative base, the 71-year-old billionaire supports same-sex marriage and the bipartisan effort that Rubio made to pass comprehensive immigration reform in the Senate in 2013.

In a letter to donors obtained by CNN, Singer praised the Rubio's position on higher education and welfare reform, along with his opposition to the Affordable Care Act and his support for Israel. Singer also described Rubio "the best explainer of conservatism in public life today" and the candidate best chance to defeat Hillary Clinton in the general election.

In response, the Florida senator said he was "grateful" for Singer's support.

"He's someone that's successful at raising money," Rubio told reporters at a campaign event in Iowa. "I'm grateful that, you know, when people donate to us they buy into our agenda, and I'm glad that he has and it will help us with resources. But you know, resources alone are not enough. You have to have the right ideas and the right principles and convince people that you're the right person for the job. But we're grateful to have his help, obviously."

Following Singer's endorsement, 2016 hopeful Donald Trump, who has been outspoken about the danger of big-money donors influencing elected officials, ridiculed the freshman senator for receiving Singer's endorsement.

"I see Marco Rubio just landed another billionaire to give big money to his Superpac, which are total scams. Marco must address him as 'SIR'!" Trump tweeted Saturday morning.