In the last week, the Republicans’ Obamacare repeal effort failed on the Senate floor despite President Trump urging GOP senators to vote yes. The White House underwent rapid and chaotic staff changes. And Congress expressly went against the wishes of a president of its own party by overwhelmingly approving more sanctions against Russia in response to its meddling in the 2016 election.

So, are we looking at a weak presidency?

Much gets written and said about presidential power, but it’s tricky to nail down what the concept really means. Presidents have lots of powers they can use on their own, including executive orders and other unilateral tools. And they can use these tools under any conditions — Trump’s ability to sign an executive order, for instance, remains undiminished. But when people talk about a president’s power, what they really tend to mean is his ability to influence other political actors, particularly Congress. And political science research has a few things to say about when and how presidents exert that influence.

The circumstances under which Trump came into office were always likely to limit his ability to sway Congress, but the administration’s actions since the inauguration haven’t helped.

The classic insight about presidential power came from the late Richard Neustadt in a book first published in 1960, in which he argued that “presidential power is the power to persuade” (an idea he attributed to Harry Truman) and identified the president’s professional reputation among Washington elites and, to a lesser extent, his standing in the public eye, as key sources of the president’s ability to influence others. Presidential power, according to Neustadt, is a process of bargaining. Successful negotiations would make subsequent successes more likely by enhancing the president’s prestige both in public and in legislative circles. Bargaining also requires understanding legislators’ incentives and being able to read public opinion, Neustadt wrote.

Under Neustadt’s definition of power, it can be hard to observe the exercise of presidential power while it’s happening, but last week’s debacle over transgender individuals serving in the military provides a pretty good illustration of how it works — and doesn’t. Trump appeared to enact the ban as part of a deal to get Congress to fund part of a border wall. But the tactic was ineffective because it drew significant backlash — some of it from military leaders, who hadn’t been consulted. Congressional reaction to the ban, even among Republicans, was tepid. The outcome of this battle is still uncertain — the House approved the funding Trump is looking for, but the bill still has to clear the Senate. In the meantime, Trump frustrated members of his own Cabinet and party with an announcement that may never lead to real policy change. It remains to be seen whether the tradeoff will be worth it in the long term.

More contemporary political science research has focused on political conditions in general, rather than the individual officeholder’s skills and traits, as the main determinant of a president’s influence on Congress. A president’s popularity does matter — research suggests that it can help him influence Congress, depending on the issue — but even the most popular and charismatic president can’t fundamentally alter the political environment, and members of Congress will generally respond to their own political incentives.

What do we mean by the political environment? Although it’s somewhat difficult to disentangle the various factors, electoral strength and party backing matter to some degree. While presidential “mandates” are more myth than reality, there is some evidence that Congress is more amenable to the president’s agenda if they think the election was understood as a mandate for it. In other words, a president who won the White House in a rout after campaigning on a clear platform — think Lyndon Johnson running on Great Society policies in 1964 — is likely to have an easier time getting Congress to do what he wants than a president who campaigned on generalities and limped into office with only a plurality of the vote — think Bill Clinton in 1992, when he won 43 percent of the popular vote with a compelling personal story and a vague-ish message about improving the economy.

And while presidents’ parties don’t always march in step with the White House agenda, partisanship can count for a lot. Even within Jimmy Carter’s White House, which was notorious for clashing with Congressional Democrats, party loyalty guaranteed a certain amount of support.

This means that Trump came into the White House at a disadvantage. Although his victory has sparked a lot of interest in why he won, the fact remains that he won fewer votes than Hillary Clinton and a below-average share of the Electoral College for a winning candidate. He also won with much less support from his own party than most newly elected presidents have received. Moreover, he articulated plenty of positions that were at odds with the GOP’s usual stances (and sometimes at odds with his own previous statements). This is especially true on health care: During his campaign, Trump promised to cover more people for less money, but that’s not what the House and Senate bills did, according to Congressional Budget Office estimates of their impacts.

Finally, while the political conditions go a long way toward determining how “strong” a president is, the White House needs a certain amount of organization to take full advantage of them. First, when it comes to policy, the main advantage that the president has over Congress is coordination. While Congress has to balance the ideas and opinions of 535 people, the executive branch can theoretically speak with one voice. Here the problems within Trump’s White House are about more than optics. A disorganized White House will have trouble developing a clear policy agenda, setting priorities and coming up with ideas about how to achieve them. A troubled communications apparatus — like, for example, one where the communications director goes on an expletive-filled tirade to a reporter and gets fired after less than two weeks on the job — will have a hard time selling the president’s agenda to Congress and the public. While we see the end product — speeches, press conferences and, more recently, social media — presidential communication involves hundreds of people and requires focused coordination. Direct communication with the public is a major asset for presidents, but without effective organization, they forfeit this advantage.

Trump, like all presidents, doesn’t have control over most of the levers that affect his ability to influence Congress. Presidents can only shape political conditions so much. But the levers he does have direct control over — his message, his organization — are being pushed in the wrong direction. And the levers on which he has a more indirect effect — public support, party backing — are also going the wrong way. Trump, in other words, has made a difficult situation worse. A strong presidency is built on more than just tough talk. Good organization may not get people chanting at a campaign rally, but it’s a big part of what makes a presidency effective.