Wednesday night's vote in the Greek parliament leaves Prime Minister Alexis Tsipras in an even more precarious position than before. Nearly 40 Syriza lawmakers abstained or voted against the reform program he had agreed upon with Greece's creditors over the weekend, meaning the vote had to be carried by the more centrist opposition parties. Tsipras' government now looks to the future with the knowledge that almost a third of its 149 parliament members do not support its current course, and that number could easily grow as the weeks pass. Meanwhile, the European Central Bank surprised some observers Thursday by raising its liquidity assistance by 900 million euros ($979 million), which will give Greek banks some respite without letting them get too comfortable — they will need more when the ECB evaluates the situation in a week.

The weekend's negotiations were the moment when Greece's leader finally capitulated to its creditors in the hope of lifting the siege of the previous six months, and yesterday's vote followed through on promises made. But the creditors' are wary of a Greek relapse, particularly because the ECB's utility as a weapon is not inexhaustible.

The bank is supposed to be the central bank for every country in the union, including Greece. It must not appear to make political decisions favoring one country over another. Of course, the bank ultimately has the entire union's best interests at heart, so it has repeatedly used its liquidity assistance as a pressure point that creditors can squeeze on unruly eurozone members. The European Court of Justice's recent judgment suggesting that the ECB should de-politicize was supposed to end this notion, but once again the provision and removal of emergency liquidity assistance have dominated this latest eurozone crisis. The bank has been careful to find an economic justification for every decision it has made, but the bank becomes less flexible every time it acts under seemingly political motivations. There is a limit to the number of times emergency liquidity assistance can be tightened and loosened in rapid succession in response to Greek political movements before the bank's political rationale is exposed.

This time, however, the ECB has seen fit to reward Greece's good behavior with a minimal loosening of the spigots. It seems almost like obedience training — a small reward to encourage similar actions in the future. But such good behavior is by no means guaranteed. Not only do the rebels in the Greek ruling party not support the terms that Tsipras agreed to in Brussels, but even Tsipras criticized them as "blackmail," explaining that they represented the least bad of two terrible options, the other being a disorderly exit from the eurozone. This is hardly a promising basis for a committed adoption of economic reforms.

But emergency liquidity assistance is not the only stick the European Union is using to keep Greece in line. Another is in the hands of German Finance Minister Wolfgang Schaeuble, who suggested to his Greek counterpart over the weekend that a temporary Grexit is an option. He has not shied from publicly restating the idea in the week that has followed. From the Greek perspective, both Tsipras and former Finance Minister Yanis Varoufakis have said that Greece is not in a position to float its own currency, meaning that a sudden Grexit could be calamitous.

So the Tsipras government enters a particularly difficult period. The twin threats of banking collapse and Grexit brandished by the ECB and Schaeuble constrain the government, and yet dissenting members of its own party are undermining its power. The temporary solution to these problems is likely to be a government reshuffle, as the more radical elements are moved out and replaced with moderate equivalents. It will need to be done carefully, however, since public opinion is also a factor.

The Greek public voted Syriza into power in January on the promise of better terms from the creditors; it also voted "no" in a referendum this month with the same goal. What it received in return was worse terms. At this stage, the public — seemingly weary from years of drama — supports these terms and reforms, but that attitude is liable to change. If Syriza were to weed out the radicals and become too moderate, the coalition that is left behind might come to be seen as just another establishment party that cannot be trusted, and public support could shift to other radicals such as the Communists, fascists or even a party of newly liberated former Syriza rebels.

The situation in Athens is fluid and uneven. There is a constant possibility that the Greek government may crumble, and public opinion is in danger of turning against the ruling party. Early elections cannot be ruled out either. We enter the weekend with many aspects clear around the Continent, but in Greece the situation is extremely unstable.