Republican Donald Trump campaigned on a promise to shake up Washington and as president the brash real estate mogul will be in a position to dramatically change how the United States handles immigration, trade and a range of other policies.

Yet many of his more ambitious proposals will require cooperation from Congress after he takes office on Jan. 20. While he will may enjoy a post-election honeymoon with congressional Republicans, a long-lasting romance is far from guaranteed, given his uneasy relationship with congressional leaders and some basic ideological differences he has with Republican orthodoxy.

Following is an overview of Trump’s top policy plans:

Trade

In his campaign, Trump argued that international trade agreements had hurt U.S. workers and the country’s competitiveness. He has promised to “get tough” on China and withdraw from the 12-nation Trans-Pacific Partnership, or TPP, which is still not finalized. As president, Trump does have some power to raise tariffs on countries such as China.

President Barack Obama’s administration has suspended its efforts to win congressional approval for TPP, saying its fate was up to Trump and Republican lawmakers.

Trump has also said he would renegotiate or scrap the North American Free Trade Agreement, the 1994 free-trade deal with Mexico and Canada. Both Canada and Mexico have indicated they are willing to discuss the agreement with Trump. Canada has indicated it would consider a free-trade agreement that excludes Mexico.

Economists have warned that such moves would damage the economy by forcing consumers to pay dramatically higher prices on everything from refrigerators to T-shirts. U.S. exports, such as airplanes and soybeans, would likely suffer as well.

 

Immigration

Trump has promised to build a wall along the Mexican border, deport millions of undocumented immigrants and ban immigration from countries that have been “compromised by terrorism.”

Since his election, he has said parts could be a fence instead of a wall, and he would act to deport up to 3 million immigrants in the country illegally who have criminal records. It was unclear where his figure comes from. Think tank Migration Policy Institute estimated in a 2015 report there were 820,000 unauthorized immigrants with criminal records.

Those policies would not come cheap. Trump has estimated the wall would cost $8 billion to $12 billion. Other estimates have run much higher.

Politico estimated it would cost at least $166 billion to deport all of those in the country illegally and complete a border wall. While many congressional Republicans support those policies, they might blanch at the cost.

Trump has said he would force Mexico to pay for the wall, but he has no power to force another country to spend money on something it does not want.

Trump also promised to withhold federal funds from “sanctuary cities” such as New York and Los Angeles that shield people who are in the country illegally.

More broadly, Trump could shift the broader debate over immigration, empowering skeptics like Republican Senator Jeff Sessions of Alabama who want to reduce overall immigration levels and reduce the number of skilled guest workers. That would be a blow to business groups and Hispanic advocates who have sought to relax immigration laws.

Healthcare

Trump has promised to repeal President Barack Obama’s signature Affordable Care Act, popularly known as Obamacare, and replace it with a plan that would give states more control over the Medicaid health plan for the poor and allow insurers to sell plans nationally.

He would need Congress to act, and Republicans could have difficulty getting the 60 votes needed to advance a repeal effort through the 100-member Senate.

Republicans could face a public backlash if they repeal a law that has provided healthcare to millions of Americans who previously had no healthcare.

After the election Trump said he would consider retaining parts of Obamacare, including provisions letting parents keep adult children up to age 26 on insurance policies and barring insurers from denying coverage to people with existing conditions.

Taxes and Spending

Trump has vowed to make deep tax cuts, while also promising to protect popular health and retirement programs that account for more than a third of U.S. government spending.

That combination of policies would massively increase the national debt, according to the nonpartisan Center for a Responsible Budget.

He has also proposed increasing spending on the military and infrastructure, but has said he would reduce spending on categories other than health and retirement by 1% each year.

On taxes, he would get plenty of help from Republicans in Congress, who have been laying the groundwork for a tax-code overhaul that would lower rates and close loopholes. But they will encounter fierce resistance from homeowners, businesses and other interest groups that benefit from current tax breaks.

Trump’s promise to protect entitlement programs such as Social Security and Medicare will rile fiscal conservatives, who worry they will swamp the federal budget in the decades to come. But those programs are popular with the American public.

Wall Street Regulation

Trump has promised a “dismantling” of the 2010 Dodd-Frank financial reform law enacted following the financial crisis, but has given few details.

Both Trump and the Republican Party have called for reinstating Glass-Steagall, the 1930s-era law that forced the separation of investment banks from deposit-taking institutions.

Republican lawmakers have so far been unable to undo many of their most-despised pieces of the Dodd-Frank law, and many in their ranks oppose a return to Glass-Steagall.

Trump appears to be leaning toward weakening the law in a manner similar to what was proposed in a bill known as the CHOICE Act this summer by Jeb Hensarling, the Republican chairman of the U.S. House Financial Services Committee.

Islamic State

Trump has offered few details about his plans to fight Islamic State but has said he would “knock the hell out of” the militant group. He says he is keeping the details of his strategy a secret so as not to disclose them to the enemy. Trump said that if he won, he would give U.S. generals 30 days after taking office on Jan. 20 to propose their own plans.

Trump has said he opposes accepting refugees fleeing violence in Syria, and instead has said he would create “safe zones” there, which he says would be funded by Gulf states.

Obama has said a safe zone in Syria would require a large U.S. military commitment, something that could prove to be unpopular with Americans weary of lengthy wars in Iraq and Afghanistan.

Russia

Trump has said he would have a “very, very good” relationship with Russia.

Trump has said could work with Russia to combat Islamic State. He also said he would look into recognizing Crimea, seized from Ukraine in 2014, as Russian territory and lifting sanctions on Russia imposed by Western nations for what they called an illegal land grab.

Trump has criticized the North Atlantic Treaty Organization, saying some U.S. allies have not met their defense commitments. In July, he said if Russia attacked a NATO member, he would consider whether the country has paid up before providing defense.

NATO leaders say the sanctions against Russia are key to persuading it to change that country’s behavior in Ukraine, where it has backed ethnic Russian separatists, and that the alliance has long been focused on fighting international terrorism.

Supreme Court

With one vacancy on the Supreme Court and several more possible in the coming four years, Trump will have a chance to put a conservative stamp on the courts for decades to come.

His list of potential nominees has won praise from conservative activists and Republicans in the U.S. Senate, who will be eager to help him in that area.

Climate Change

Trump has called global warming a hoax and said he wants to cancel the 2015 Paris Agreement among almost 200 nations that entered into force on Nov. 4. Instead, he says he will push ahead and develop cheap coal, shale and oil.

Trump’s advisers are considering ways to bypass a theoretical four-year procedure for leaving the accord, according to a source on his transition team.