WASHINGTON – Nancy Pelosi, who took the gavel as House speaker Thursday, told USA TODAY in an exclusive interview that President Donald Trump can expect a “different world” from the first two years of his presidency when the GOP controlled both chambers of Congress.

The California Democrat plans to confront Trump on many fronts, from investigating the deaths of immigrant children in U.S. custody to demanding Trump’s tax returns and protecting special counsel Robert Mueller’s Russia investigation.

Those clashes loom as Pelosi and her Democratic colleagues remain locked in a budget and border security battle with Trump that has left parts of the federal government shut for nearly two weeks.

The election of speaker was one of the first orders of business for the new Congress sworn in Thursday, when Democrats took control of the House for the first time in eight years.

Trump warned that investigations of him and his administration would lead to a “war-like posture” in Washington. The new speaker made clear she won’t shrink from a fight.

“He was used to serving with a Republican Congress, House and Senate that was a rubber stamp to him. That won't be the case,” Pelosi said in the USA TODAY interview just before the holidays. “Oversight of government by the Congress is our responsibility.

“That's the role that we play."

Despite calls from some on the left wing of her party to try to remove Trump from office, Pelosi said the efforts to serve as a check on Trump’s power don’t extend to impeachment – at least not yet. She remains intent on protecting Mueller’s investigation into whether the Trump campaign coordinated with Russia in the 2016 election.

More:In Trump era, Nancy Pelosi admits to nostalgia about George W. Bush. Here's why

More:Nancy Pelosi and Jim McGovern: House Democrats will restore transparency, ethics, unity

More:Here's what Democrats will do to immediately change the House

“If there's to be grounds for impeachment of President Trump – and I’m not seeking those grounds – that would have to be so clearly bipartisan in terms of acceptance of it before I think we should go down any impeachment path,” Pelosi said.

“I keep coming back to the same word: the facts,” she said. “The facts will indicate a path, and I don't think we should impeach a president for any political reason, but I don't think we can ignore any behavior that requires attention and that was all based on the facts.”

One of the first moves Democrats will take to try to check the power of the White House and Republicans will be the unveiling of an anti-corruption bill designed to ease obstacles to voting, curb the role of big money in politics and hold politicians and government officials to higher ethical standards. The plan's supporters want to require presidents to release their taxes – something Trump has refused to do.

Newly armed with subpoena power, Democrats are likely to investigate potential conflicts of interest between Trump’s businesses and his role in setting policy for his administration, as well as possible ties between the Trump campaign and Russia and whether Trump and his family have financial ties to Russia. Democrats are also likely to subpoena Trump’s tax returns.

Jim Manley, a former aide to Senate Democratic leader Harry Reid, said oversight of the Trump administration will be a “target-rich environment,” but as speaker, Pelosi will have an important role in guiding the broad parameters of the investigations.

“She’ll give the chairmen wide latitude, don’t get me wrong, but it’s all going to be coordinated by the leadership,” Manley said. “That’s just how she rolls.”

'War room-style effort'

For the past two years, members of Pelosi’s team have held weekly strategy meetings with top policy and communication staffers from several committees with oversight powers. They have focused on exposing scandals among administration officials who have since left their positions, allegations of Trump’s conflicts of interests, the handling of security clearances and aspects of the Russia investigation.

“Given the magnitude of the corruption, cronyism and incompetency in this administration, it’s definitely a war room-style effort,” said Ashley Etienne, a Pelosi spokesperson who leads communication work on oversight for Democrats.

As House speaker from 2007 to 2011 and as minority leader before and after that, Pelosi, 78, named close allies to the House Intelligence Committee, the only committee whose membership is controlled by party leaders and the committee that’s the central player in the Russia investigation.

She is a former ranking member of the committee, and she may be more “deeply involved” in its work than any other, said Rep. Adam Schiff, D-Calif., the incoming chairman.

Her involvement isn’t at the level of specific investigative threads or witnesses, he said. It’s more at the level of the “Gang of Eight,” the intelligence committee and party leaders who are briefed on covert actions.

When it comes to protecting the Mueller investigation, her position is part of a "consensus," said Rep. Jerrold Nadler, D-N.Y., the incoming House Judiciary Committee chairman.

"Nancy certainly agrees with that, and she pushed that," Nadler said.

Caution on impeachment

Pelosi’s own caution about impeachment hasn’t stopped some Democrats from twice voting for impeachment. A House resolution was defeated 355 to 66 on Jan. 19, 2018.

The group Need to Impeach, which is headquartered in her district and funded by billionaire activist Tom Steyer, gathered 6.5 million signatures in support of impeachment – and expects Pelosi to come around.

“The Democrats nationally want action around Trump,” said Kevin Mack, lead strategist for Need to Impeach. “We as a party have to prove that we can represent Democratic values. So I don’t think Nancy Pelosi can be a speed bump on impeachment forever.”

Others said part of her caution about impeachment comes from watching Republicans go after President Bill Clinton during the Monica Lewinsky scandal – and lose House seats in 1998. The House, then dominated by Republicans, voted to impeach Clinton after the election, but he was acquitted by the Senate.

GOP pollster Frank Luntz said Americans could welcome the oversight of the Trump administration if they feel it is being done for the “right reasons.”

On the flip side, Luntz said, "If they think it’s oversight for political gain, they will reject it."

Trump has sought to rally his political base by portraying Democrats as intent on taking him down. Alex Conant, a former aide to Sen. Marco Rubio, R-Fla., said Clinton benefited from "overzealous" Republicans during the Lewinsky scandal.

Because of that, Conant said, Pelosi will need to walk a fine line.

“Pelosi’s role will be to negotiate big policy matters with the White House ... and then to try to limit and guide the investigations behind the scenes,” said Conant, a White House spokesman during President George W. Bush's second term. “Clearly, the Trump administration would love nothing more than for Democrats to overreach and go on fishing expeditions.”

Pelosi is not only the first woman to become House speaker but she is one of just a handful of people who won multiple terms in the post.

She is admired by some in the party for her legislative prowess. Getting Obamacare over the finish line is one example of that.

Former President Barack Obama said in November on "The Axe Files" podcast that Pelosi isn’t always the best on a cable show “or with a quick soundbite,” but he called her an “extraordinary partner” and praised her as “one of the most effective legislative leaders that this country's ever seen.”

Coastal elite caricature

She’s seen by Republicans and some Democrats as the personification of a coastal elite. Her Hawaii trip during the government shutdown fed into that criticism.

During the 2018 midterm campaign, the GOP ran constant ads hammering her, pointing out that her favorability rating was underwater. An NBC News/Wall Street Journal poll from mid-December had her at 41 percent unfavorable, 28 percent favorable. That same poll had Trump at 52 percent unfavorable, 37 percent favorable.

The campaign featured scathing attacks on Pelosi from Trump and Republicans. Even some Democrats sought to distance themselves from Pelosi. She worked on strategy behind the scenes and hauled in $135.6 million for Democrats this cycle, including $129 million directly for the Democratic Congressional Campaign Committee, according to her office. She prevailed, and Democrats won a net gain of 40 seats.

Pelosi has historically “appeared to be proper and relied on this grandmother image,” but she’s actually a “very strong, determined woman,” said Rep. Jackie Speier, D-Calif. Her relationship with Trump will be “a stunning dynamic to watch,” Speier said, because Trump hasn’t had to deal with anyone like her before – a mother of five children who knows how to deal with "bratty behavior."

“The president has been successful in bullying people into doing things – that’s how he makes his deals,” she said. “He’s got to change his strategy, or he will fail.”

After Democrats won the House, Pelosi faced opposition in her bid for speaker, but she stamped out a centrist rebellion by agreeing to limit her term to just four more years. Rep. Marcia Fudge, D-Ohio, considered challenging Pelosi for the top spot – until Pelosi announced that Fudge would chair a subcommittee focused on elections and voting issues, one of her signature issues.

Republicans grudgingly admire her toughness and ability to hold her caucus together. Pelosi “plays the blood sport of politics” better than the past three GOP speakers, said Tim Cameron, a Republican strategist who worked for the House GOP conference under Speaker John Boehner.

“Her ability to dispel potential rivals is literally unrivaled,” Cameron said.

“I think every Republican speaker since 2010 has been jealous of what she was able to get done from 2006 to 2010. She never really had the issues that we had with the conservative wing of the party,” Cameron said.

Lecturing Trump

Though much of Pelosi's legislative dealmaking is done behind the scenes, the country witnessed her latest toe-to-toe battle with Trump on government funding during a televised meeting Dec. 11 in the Oval Office.

Republicans pounced on Pelosi for saying the GOP didn’t have the votes in the House for a border wall. The House passed $5.7 billion in funding for the wall Dec. 20, but the bill didn't get a vote in the Senate, and Senate Minority Leader Charles Schumer, D-N.Y., called on Trump to "abandon the wall."

Pelosi told USA TODAY that the House vote was another example of Trump’s “rubber stamp Congress.”

“I know that many of them did not really believe in that, but they gave him the vote anyway, for whatever reason,” she said.

Pelosi’s allies pointed to that Oval Office meeting – when the president said he’d be “proud” to shut down the government – as the latest example of Pelosi holding her own. She lectured Trump on negotiating with Congress, then donned sunglasses as she left the White House, in a moment that lit up the internet.

Speier recalled attending a holiday party with Pelosi the weekend after the meeting with the president. Women approached the pair to thank them for their work and compliment Pelosi for standing up to Trump.

“I said, ‘We’re sassy,’ ” Speier recalled to USA TODAY. “And then Nancy says, “No, we’re badasses.’ ”