In the wake of his strong showing in Iowa, Marco Rubio is gaining momentum among the lobbyists and big-time donors who can super-charge his campaign heading into a crucial stretch.

The Rubio campaign said it raised $2 million in the 24 hours after Iowa, where he placed third behind Ted Cruz and Donald Trump.

Behind-the-scenes, money is flowing to the Florida senator from those with ties to the lobbying business — who often contribute big checks to super PACs supporting candidates or bundle money from their friends and colleagues to give directly to campaigns. Some of those donors previously contributed to a pro-Jeb Bush super PAC, Right to Rise, which only took in $15 million in the second half of 2015 compared to $103 million during the first half.

Rubio is the only presidential candidate whose financial support from Washington lobbyists appeared to grow over time in 2015 and his fundraisers say the momentum is accelerating, post-Iowa.

Rubio received about $670,000 from lobbyist bundlers during the final three months of 2015 — a steady uptick from the $365,600 he raked in during the third quarter, and the $133,450 he collected during the second quarter. The two other candidates receiving contributions from lobbyist bundlers, Hillary Clinton and Bush, either saw such contributions decline throughout the year, or fluctuate. Clinton raised $717,00 during the fourth quarter. Bush raised $196,000.

The lobbyist money could help Rubio shore up his standing in the so-called establishment lane as he heads into the New Hampshire and South Carolina primaries — especially against former Florida Gov. Bush, who also has a donor base in the Sunshine State.

A pro-Rubio super PAC, Conservative Solutions, saw a spike in donations from lobbyists during the second half of 2015 compared to the first half of the year. The super PAC raked in about $60,800 from 10 lobbyists and firms, almost exclusively from Florida, during the second half of the year. That is far more support than it got from the industry during the first half of the year, when it did not list any lobbyist donors. It also got a major boost, $500,000 in September, from coal executive Chris Cline, who earlier in the year contributed $1 million to a super PAC packing Bush.

The super PAC recently picked up sizable contributions from at least two individuals with ties to the lobbying business who previously gave to a pro-Bush super PAC: Cesar Alvarez, co-chairman of the law and lobby firm Greenberg Traurig; and Brian Ballard, founder of the Florida lobby firm Ballard Partners.

Ballard, a lobbyist and prominent fundraiser, gave $20,000 to a Bush-affiliated super PAC in March before switching his allegiance to Rubio in November — at which time he gave a Rubio-allied super PAC $25,000.

Ballard said he got more than a dozen phone calls the day after the Iowa caucus, including from some Bush supporters expressing interest in contributing to Rubio’s campaign.

“People are coming to me and asking, ‘How can I contribute?’ which is a nice change,” Ballard said. “Before Iowa, we’d have to make the call. Now, people are calling us.”

Some potential donors are now more willing to bypass the conventional meetings and fundraisers to contribute directly, said Ballard, who was Florida finance co-chair for John McCain and Mitt Romney.

“What I’m finding more now is people don’t have to do the meeting or the event. They’re like, ‘How can I get my contribution to the campaign or super PAC?'” he said. “That’s refreshing, that’s the new part. They’re willing to just donate and be part of the tide that seems to be developing.”

Ballard is also a lobbyist for Trump, representing the Trump Organization’s interests before the Florida legislature.

Alvarez, an attorney in Miami, is not a lobbyist, but his firm has a well-known Washington lobbying practice. Alvarez gave a pro-Rubio super PAC $10,000 in November, after giving Right to Rise $45,000 in March, according to Federal Election Commission filings. He has also given smaller amounts to both candidates’ official campaigns throughout 2015.

A spokeswoman for Greenberg Traurig said Alvarez is an independent who contributes to members of both political parties, and considers both Rubio and Bush friends.

“Both candidates have been friends prior to the race and will remain so following the race,” Alvarez said. “I am a registered Independent and give to candidates of both parties as well as candidates in the same race, as I have here, and allow the American public to decide.”

Though lobbyists typically do not give huge sums to campaigns, especially compared to billionaire donors, they are part of the political establishment and their support often has ripple effects outside the Beltway, influencing executives at companies whose interests they represent in Washington.

Individuals giving smaller amounts to Conservative Solutions include two other professionals in the government affairs space who previously gave to Bush.

Chris Dorworth of the Florida lobby shop Ballard Partners, gave Rubio’s super PAC $7,300 in December after giving $2,500 to Bush’s super PAC earlier in the year. And Chris Henick, a Republican strategist and former George W. Bush White House adviser, gave $500 to Rubio’s super PAC after previously giving to Bush and Chris Christie.