WASHINGTON (AP) — The sprawling network funded by the billionaire Koch brothers is having a very good run with President Donald Trump in the White House and Republicans in control of Congress.

Tax cuts are now signed into law. A conservative judge is seated on the Supreme Court. And many governmental regulations, including those on labor and environmental practices, are facing rollbacks.

That success is starting to get attention. Democrats are increasingly questioning how far the network's influence extends into the White House, casting the groups' backing by industrialists Charles and David Koch as puppeteers behind Trump's agenda and hoping to rouse their own donors to fight back. The network in turn is ratcheting up its focus on areas where it aligns with Democrats — most notably immigration legislation — and reviving calls for bipartisanship.

"We've come off one of the most successful years in our network's history," said James Davis, executive vice president of Koch-backed Freedom Partners and a spokesman for the Seminar Network, the broader organization of groups and donors. "And we're going to turn up the heat on both parties to drive forward."

But there's another outcome, too: Sen. Sheldon Whitehouse, D-R.I., and other senators recently fired off letters to the administration asking for a detailed accounting of the network's role at various government offices including the Environmental Protection Agency, the Labor Department and the Department of Veterans Affairs. The senators name more than a dozen individuals working in the administration with ties to the groups. On Monday, the lawmakers will launch a series of Senate floor speeches turning a spotlight on the influence.

"Americans have a right to know if special interests are unduly influencing public policy decisions that have profound implications for public health, the environment, and the economy," wrote Whitehouse with Sen. Ed Markey, D-Mass.; Sen. Catherine Cortez Masto, D-Nev.; Sen. Elizabeth Warren, D-Mass.; Sen. Ron Wyden, D-Ore.; and Sen. Tom Udall, D-N.M.

"There are plenty of billionaires these days, and a bunch of them do pretty good stuff," Whitehouse is expected to say in Monday's speech, according to excerpts. But he's highlighting a subset he says is "trying to quietly remake America to their ideology."

The influence of the Koch-backed groups is somewhat surprising. They are an array of organizations and include Americans for Prosperity, Freedom Partners and Concerned Veterans for America, whose donors comprise some of the wealthy attendees of the twice-a-year Seminar Network conferences.

The groups took a pass on donating to Trump's Republican presidential bid. But they have managed to influence policy through several top allies in key jobs sprinkled across the administration.

Among those in the Koch orbit with ties to the administration, perhaps the most prominent is Marc Short, the White House director of legislative affairs, who is a past president of Freedom Partners, the network's chamber of commerce-styled group. Short plays a key policymaking role and is a Capitol Hill fixture of legislative battles. The senators mention several others with top policy roles, including Kellyanne Conway, a counselor to the president.

Koch groups have been central to Trump policies Democrats oppose — among them tax cuts for the wealthy, loosening of environmental regulations and expanding private-sector health care for veterans. Trump's first-year regulatory rollbacks were drafted by one of the Koch-backed groups and became a ready blueprint for action in Congress.

The network, however, doesn't just toe the Trump line. On Monday, the group is stepping up its effort to push Congress not to let up on legislating as lawmakers turn to focus instead on campaigning for midterm elections.

Two groups in the network are releasing a letter to congressional leaders of both parties, urging them to take up a bipartisan compromise to help young immigrants, known as "Dreamers," who have been living in the U.S. illegally since childhood. They want Congress to pass a deal that was on the table earlier this year — a path to citizenship for 1.8 million Dreamers and $25 billion for border security. Because most Americans want a solution that would allow the Dreamers to avoid deportation, the group says Trump and Congress should be able to come up with a solution.

"There is no reason to continue to delay action on the Dreamers," wrote officials from Freedom Partners and the LIBRE Initiative, two network groups. "What are we waiting for?" The group is also pushing Congress to take up criminal justice reform, another issue with bipartisan support that has lagged.

Republicans have little appetite to engage on big-ticket items as they struggle to keep control of their majority in the House and try to pick off Democratic incumbents up for re-election in the Senate from conservative Trump-won states.

And Democrats, while saying they are willing to engage with the Koch-backed groups, are at times envious of their operation and eager to pound on their influence, which includes chapters that mimic traditional party apparatus in many battleground states.

It doesn't help build bipartisanship when much of the advocacy the Koch groups undertake, unleashing their army of volunteers and spending sums on advertising, ends up going against Democratic senators in Missouri, Wisconsin, North Dakota and others in tough election battles.

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Follow Lisa Mascaro on Twitter at https://twitter.com/LisaMascaro