As President Donald Trump prepares to give his first major address to Congress Tuesday night, the Republican legislative agenda appears to be floundering, with neither the president nor GOP leaders anywhere close to having the votes lined up to pass Obamacare repeal or tax reform.

To buoy the effort, Republicans on Capitol Hill want Trump to do ... well, something.

Some are demanding more guidance and specificity from the president. “It’s hard to see how this [Obamacare repeal and replace] gets done unless the president says, ‘OK, let’s do it this way,’” Sen. Lamar Alexander (R-TN) told Politico earlier this month. “We’ve got our own ideas and we’ll pass our own bill, but it’s hard to do anything this complex unless the president is directly involved.”

Others — particularly party leaders such as House Speaker Paul Ryan — appear to want more blessings than details. That is, they seem to want Trump’s support of what leadership already plans to do. Per CNN, Ryan planned to ask Trump in a private meeting Monday to use the speech to signal his approval for the House GOP leadership’s still-in-development Obamacare plan.

Though Trump will have an opportunity to take either path during his speech, so far he has done neither. Despite repeated promises, he hasn’t released his own tax or health care plan. But he also hasn’t clearly signaled that he’ll rubber-stamp whatever comes out of Congress.

Partially because of that presidential limbo, plans for the repeal and replacement of Obamacare, GOP leaders’ top priority in Congress, are in disarray. No bill has yet been released, and estimates about the effects of some proposals being considered are grim. As Obamacare supporters turn out in large numbers at congressional town halls across the country, Republicans in the House of Representatives alone are deeply divided about what the legislation should look like. Challenges in the Senate look even more serious, particularly because at least eight Democratic votes would be needed for a full “replacement” bill.

Now, per the Wall Street Journal, Ryan’s current plan to pass repeal is essentially to just put out a bill and dare his own members to vote against it (as conservatives are already threatening to do). But this is not how major legislation usually happens.

To pass Obamacare in the first place, Congress and President Barack Obama engaged in a months-long process in which reform was considered and amended by various committees and again on the floor — a process that allowed time to assuage the concerns of many stakeholder groups and swing-vote members.

Such a process is generally believed to be crucial to building the broad support a major bill needs to actually pass. Throwing something up quickly without building the necessary support for it seems to have a very high chance of failing — and even if something does get rammed through the House, its prospects in the Senate would be very dubious.

And failing to build that support for a repeal and replace bill is delaying the second big item on the GOP’s legislative wish list: tax reform. The idea here is that Republicans want to pass a major tax code overhaul, but for both political and procedural reasons they’d prefer to do it after Obamacare repeal (which would include a big tax cut for the rich) is signed into law. If they can’t get Obamacare repeal done, they’d probably have to rethink their plans on taxes overall.

Even on taxes, the party is intensely divided. Speaker Ryan and House Ways and Means Committee Chair Kevin Brady are fans of an idea known as either the border adjustment tax or a destination-based cash flow tax. The prospects for that provision look shaky, particularly in the Senate, where, if Sen. Lindsey Graham (R-SC) is right, there might not even be 10 votes for it. Retailers and importers generally are already furiously lobbying against the idea.

Beyond these two big-ticket agenda items, congressional Republicans will also have to somehow find the votes to take care of normal business — funding the government and raising the debt ceiling — and are going to at least attempt to pass a budget. Trump will want funding for his border wall to be thrown in there somewhere. The president has also said he’d love Congress to pass a big infrastructure bill, but that now seems to have been shelved for the foreseeable future. So things are a bit of a mess.

Republicans are hoping President Trump can turn this around

Though we don’t yet know what President Trump will say during his address, he’ll likely call on Congress to take action and get to work on solving some of those problems he said were so dire during the campaign. There has been no indication that he will endorse specific congressional plans, or that he will offer detailed new plans of his own, during the speech. (Governors who attended an event with Trump this weekend claim he said his administration’s own plan was still a few weeks away.)

It may seem a bit odd that so many on the Hill are looking to Trump. After all, the president does not technically have to lift a finger to get a bill passed. Indeed, his formal powers on ordinary legislation are quite limited: When a bill reaches his desk, he can either sign it or veto it.

But according to Gregory Koger, a political science professor at the University of Miami, because of the sheer number of people in Congress — none of whom, technically, report to one another — “coordination problems” can arise.

“They can all agree on general goals, but when it comes to a proposal, they might have 200 different ideas,” Koger says. “Congress can solve its own coordination problems — that’s why it has committees.” But, he adds, “In some cases they don’t want to do it on their own, and they wait for the president.”

What the president can do to get Congress moving

To try and rack up major achievements, modern presidents and their staffers have tended to deeply immerse themselves in major legislative fights. And the consensus of several congressional experts I talked to was that some level of White House engagement is likely necessary to get anything big or controversial into law. “When there’s a very narrow margin, presidential involvement can be crucial,” says Jim Manley, who was an aide to former Senate Democratic Leader Harry Reid.

Despite their lack of formal powers to affect major legislative efforts, when recent presidents have gotten involved, they’ve tended to act in six main ways:

Setting the agenda: Presidents try to make clear which bills they want Congress to prioritize. This is a two-way street, though — if something’s not a congressional priority, a president will have a tough time prodding Congress into action. Contributing administration expertise: The executive branch is far bigger than Congress, and there are many more people in various agencies with relevant subject matter expertise. If these staffers are engaging with Congress, they can be very helpful in crafting new legislation. Fighting to craft the bill in a certain way: On some bills, presidents will deeply engage on certain sub-issues, fighting for priorities close to their hearts. If they do so, they’ll effectively become one of many players in the negotiation process. Going public to try to win over voters: Presidents can also try to use their public megaphone to try to win voter support for what Congress is doing — though in our polarized age, the risk is that by speaking out, the president could drive support away as well. Twisting arms and cutting deals to get something passed: Finally, presidents can help broker deals with different members or factions of Congress, or with relevant interest groups, to help get a bill across the finish line — a controversial process that was crucial to Obamacare’s passage. Deciding when to throw in the towel: In the face of numerous obstacles in passing the Affordable Care Act, Obama repeatedly signaled to his party that they would keep pushing ahead, rather than quit or dramatically scale back the bill in the face of opposition.

One big question: will Trump get into the weeds?

For Trump in particular — a president who has no real experience with Congress and very little apparent knowledge of policy, but who styles himself as a deal cutter — one key thing he’ll have to decide soon is just how much he cares about what’s actually in the underlying bill.

He may well decide to stay out of the weeds and cheerlead whatever Congress can agree on. “Donald Trump clearly wants to look effective,” says Josh Huder, a fellow at Georgetown University’s Government Affairs Institute. “To do that legislatively, I would allow Republicans to drive the agenda, and be behind them and support them as much as possible.”

The problem there, of course, is that Trump often hasn’t seemed to be on the same page with the congressional GOP on health policy or the border tax. He promised not to cut Medicaid during the campaign, and many in the House want to scale back the program. He’s said that everyone should be able to get insurance even if they can’t afford it, but other Republicans’ main goal is to reduce the government role in health care. And on tax reform, he and Paul Ryan seem to support entirely different ideas that merely both happen to include the word “border.”

All this poses the risk that even if Hill Republicans do make progress, the president could scramble their plans with one critical tweet or statement. And naturally, if members of Congress are afraid the president will pull the rug out from under them, they’ll be less likely to go out on a limb and support something controversial in the first place.

The main holdup isn’t Trump. It’s congressional Republicans. (Though Trump can make their problems worse.)

Still, it’s important to remember that on many of these issues, Trump is a problem for the Republican agenda, but he’s not the problem.

Mitch McConnell and Paul Ryan are experienced lawmakers, as are other members of Congress. They also have a lot more policy knowledge than Donald Trump does. Theoretically, they’re perfectly capable of drafting plans, bargaining with each other, and coming to some sort of accommodation without the president’s supervision or involvement.

They’re having a lot of trouble getting this going not primarily because Trump has been erratic, but because the underlying policy issues here are tremendously difficult and controversial — and because in its years as the opposition, the GOP never developed a serious consensus in its coalition on plausible health reform proposals.

On Obamacare, I wrote a few weeks back about the biggest issues that still divide Republicans, and they are massive. There’s little GOP unity on how much a replacement plan should cost, how to pay for it, whether the Medicaid expansion should be rolled back, how to fix the individual markets, or even what the basic goals of health reform legislation should be. (Already, conservatives in both the House and Senate are rebelling against House leadership’s leaked repeal plan, saying it doesn’t go far enough.)

As mentioned, there are similar splits on what should be done with tax reform too — though in the end the gaps may be easier to bridge there, since people’s benefits aren’t at risk.

There is no magic, “terrific” plan Trump could release that could fix those problems and heal those divisions. So rather than hoping the president will solve their problems, if the GOP does want to get anything done, it should get started on the difficult process of legislating — of proposing bills, debating them in committees, and trying to come up with the compromises that can actually forge something that could win the support of majorities in both chambers. A Donald Trump speech is no substitute for all that.