The super PAC supporting Sen. Marco Rubio's presidential bid raised $16.1 million since the Florida Republican entered the 2016 primary in mid-April.

Conservative Solutions PAC, run by Republican operatives with ties to Rubio's campaign team, announced that it had banked just under $16 million as of June 30, and said the money raised beat the organization's expectations.

Earlier this week, Conservative Solutions Project, super PAC's nonprofit affiliate, revealed that it had raised nearly $16 million since April, giving the two pro-Rubio outside groups more than $30 million at their disposal to invest in his presidential candidacy.

"We've definitely benefited from the strong response to Marco Rubio's first few months on the campaign trail, allowing us to exceed all our goals for the first half of the year. More than that, things are setting up very well for the second half of the year, ensuring we'll have the resources we need to share Marco's conservative vision with voters. Donors see what Hillary Clinton sees, that no one matches up better against her, no one is better positioned to defeat her, than Marco Rubio," Warren Tompkins, a senior official at Conservative Solutions PAC, said in a prepared statement.

Federal law prohibits super PACs and campaigns from coordinating. But these third party groups can accept donations in unlimited amounts, making them a crucial part of any presidential candidate's coalition of supporting political organizations. Individual contributions to a candidate's official campaign committee are not permitted to exceed $2,700. With so many top tier contenders running for the Republican presidential nomination, the competition for super PAC dollars has become as fierce as the race for campaign cash.

Disclosure: The author's wife works as an adviser to Scott Walker.