Rep. Devin Nunes has become a fundraising geyser, raising approximately $5 million in the second quarter from tens of thousands of grassroots contributors who are rewarding the California Republican for defending President Trump against suggestions that he colluded with the Russians to win the White House.

Nunes, chairman of the House Select Committee on Intelligence, closed the period with $6.1 million in cash on hand to spend on his re-election campaign. The congressman's second quarter haul is nearly three-and-a-half times the remarkable $1.25 million he raised in the first three months of the year, and comes after his political team invested in a national small-dollar fundraising program that kicked off after the House Intelligence Committee completed it's investigation into the 2016 presidential campaign.

Sources shared Nunes' figures with the Washington Examiner on Sunday, just prior to Midnight, Federal Election Commission disclosure deadline.

Nunes at mid-year had raised around $6.25 million; the congressman raised approximately $1.25 million in all of 2017, before he earned a reputation as a staunch Trump defender and became the chief antagonist of special counsel Robert Mueller's federal probe into Russian meddling in the 2016 election and possible collusion by the president and his associates.

His Democratic challenger in the general election is Fresno County Deputy District Attorney Andrew Janz, who is outpacing all previous Nunes challengers in fundraising. A Democratic poll released in late June showed Janz trailing Nunes by 8 points.

The Californian has capitalized, politically, by developing a direct-mail and email fundraising program that is churning out dollars and building a national list of grassroots donors that would be the envy of any presidential campaign. Nunes' colleagues are are taking notice as well. The congressman is in-demand as a campaign surrogate, and is scheduled in the next three months to travel the country raising money for incumbents, challengers, and open-seat candidates.

Nunes is due to headline 15 different events so far, with more in the planning stages. He appeared at two candidate events this past weekend.

Nunes, 44, was first elected in 2002 and over the years developed a power base on Capitol Hill, with close ties to House GOP leadership, particular Speaker Paul Ryan, R-Wis. — they bonded years ago on their mutual support for entitlement and tax reform. Nunes established a relationship with Trump during the 2016 campaign when the then-candidate visited his Central Valley congressional district, and he later served as an adviser to the president’s transition team.

Their views on Russian strongman Vladimir Putin did not necessarily line up — Nunes has always been a Russia hawk.

But from the outset, Nunes was suspicious of accusations, mostly from Democrats but also some Republicans, that Trump colluded with the Kremlin. Even as Nunes was leading the House Intelligence Committee’s investigation into Russian meddling, his defense of the president and counterattacks on Democrats and Trump critics like former FBI Director James Comey escalated.

The Mueller investigation's indictment of Russian intelligence officers for hacking the computers of Democratic officials and committees and funneling the confidential information found to the press at the height of the 2016 campaign, revealed Friday, didn't appear to soften Nunes' criticism of a probe that Trump continues to refer to as a "witch hunt." Trump and Putin were scheduled to meet Monday in Helsinki for bilateral talks.

Meanwhile, Nunes has supervised a House intelligence panel probe of possible malfeasance by Trump’s opponents in the 2016 campaign as well as alleged impropriety on the part of the FBI and other federal officials that were involved in investigating Trump during that period.

Nunes has pressured the Justice Department to reveal confidential information about the counterintelligence investigation into the Trump campaign in 2016, and the Mueller probe, threatening top Justice officials with contempt of Congress charges if they aren’t more forthcoming.

In the process, Nunes had become a conservative media star, with periodic appearances on programs like Sean Hannity’s highly rated Fox News show and across other conservative media platforms.

This story has been updated with a more detailed account of Nunes' second quarter fundraising.