Warren, a Massachusetts Democrat who's been floated as a potential 2020 presidential contender, has been a strong proponent of increasing regulation on the banking industry. She cheered on the Consumer Financial Protection Bureau when it was first created under President Barrack Obama.
Seidel then gave a stern warning to Republicans who voted for a $1.3 trillion spending bill that was passed in March.
"If you are a Republican who sits on the committee that wrote the worst spending bill in our country's history and you voted for it, you're darn right we will hold you accountable," Seidel said.
Two Republicans who voted for the spending package, Senator Tim Scott, R-S.C., and Congressman Doug Collins, R-GA, were in attendance.
Koch himself, in a rare briefing with reporters on Sunday, also distanced himself from the idea of solely backing Republican lawmakers. He was asked by reporters if he would be OK if Democrats took over the House of Representatives during the 2018 Congressional midterm elections.
Koch replied that he hopes to see people in power who will back policies that will "move toward a society, mutual benefit, equal rights, where everybody has the opportunity to realize their full potential," he said. "I don't care what initials are in front or after somebody's name."
The public turn by the billionaire and his network against a few of the latest Republican initiatives on Sunday, including President Donald Trump's decision to implement import tariffs, is the latest in a sharp reversal by Koch away from backing candidates, and toward a policy based agenda.
In July, Americans for Prosperity unleashed a digital advertising campaign in support of North Dakota Democratic Senator Heidi Heitkamp, thanking her for co-sponsoring the Economic Growth, Regulatory Relief and Consumer Protect Act, a bill that rolls back Dodd-Frank Act regulations mainly on community banks, or those with less than $100 billion in assets. It recently passed in Congress with bipartisan support.
In May, the group unveiled a six figure advertisement onslaught targeting Democratic and Republican lawmakers who backed the trillion dollar spending package — but the majority of the ads were against GOP congressmen.
Rep. Tom Rooney, R-Fla., was among the Republicans, although he decided not to seek re-election this year. The others were Reps. Hal Rogers of Kentucky; Lou Barletta of Pennsylvania, who is challenging Democratic Sen. Bob Casey this fall; Mike Bishop of Michigan; Mike Simpson of Idaho; John Carter of Texas; Robert Aderholt of Alabama; Mark Amodei of Nevada; Jeff Fortenberry of Nebraska; and Ken Calvert of California.
As for Trump's tariff policy, Koch acknowledged that tensions between the United States and their trading partners such as the European Union and China, could turn into a full scale trade war.
"If it's severe enough it could," Koch said.
CORRECTION: This article has been updated to reflect Sen. Tim Scott represents South Carolina.