The presidency and both houses of the US legislature are currently controlled by the Republican Party, one of the two main political parties in the United States. This situation may help the party pass laws that support its principles, but that does not mean that proposals pass unhindered through Congress.

The combination of traditions, “checks and balances” and mathematics influence how a bill becomes law.

Let’s start with the mathematical component. The 435-member House of Representatives enacts laws by a majority vote, which means that at least 218 members of the lower house must vote in favor of the bill in order to be approved.

In the Senate, which consists of 100 members, the situation is more complicated. A group of senators may arrange for obstruction, or prevent the proposal from being voted on if 60 senators disagree that it is time to stop discussing this measure and vote.

For example, in the current composition of the US Senate, 52 Republicans need eight Democratic votes to overcome the obstruction and vote on the bill. When there are enough votes to put an end to the obstruction, the Senate still needs to cast an official vote to pass the bill, but this requires a simple majority (51 votes). If the bill is not controversial, and none of the senators uses obstruction, a majority vote is taken into account.

President Trump wants the Senate to get rid of the right to obstruction and move to a 51 percent majority to accept any proposal in the Senate. Otherwise, he said, few bills will be passed. Donald Ritchie, US Senate honorary historian, predicts that senators are unlikely to change the rule allowing obstruction. “This rule makes every single senator a powerful politician,” he says.

Once during an obstruction senators spoke from the rostrum all night to prevent voting. In recent years, it was enough for senators to simply threaten with obstruction so that the leadership of the upper house backs off. (Members of the majority party are not too keen to stay awake all night and watch their political opponents come out from the podium if they know they don’t have enough votes to stop this process, Richie says.)

Obstruction has a broader purpose than preventing the adoption of specific legislation. It fosters the Senate’s tendency to seek a bipartisan compromise. This makes the Senate a completely different body than the House of Representatives, where over the past 20 years the majority party has traditionally focused on legislation that it can adopt without the help of another political party.

After the Senate and the House of Representatives adopt their own bills on a specific issue, the process of agreeing two different versions begins. If the compromise variant obtained as a result of the process is approved both in the House of Representatives and in the Senate (they vote again), then after this the bill is sent to the president. The bill rarely reaches this stage, Richie points out: the American system “was not designed to be easy.” (Even when the leadership of the House of Representatives and the Senate belongs to the same party, it does not always adhere to a single opinion on this or that legislation.)

However, the rules of the House of Representatives and the Senate are not the only factor. The president and the courts also play an important role. Their activities are based on a system of “checks and balances” in the US Constitution that exist to ensure that one branch of government does not have too much influence.

When the bill is approved by Congress, it goes to the White House, where its monthly or annual journey can end with a stroke of the president’s pen. If the president signs the bill, it becomes the law.

If the president rejects the law or vetoes, this does not necessarily mean the end of the bill. Congress can overcome the president’s veto with two-thirds of the votes in both houses. This “check” does not allow the president to block the adoption of the law when he or she enjoys widespread support. History shows that Congress overcame less than 10 percent of all presidential veto.