CARACAS, Venezuela — The world is increasingly taking sides on who should be the rightful leader of Venezuela.

On one side is President Nicolás Maduro, whose socialist government is seen as increasingly corrupt, inept and repressive. On the other is the opposition led by Juan Guaidó, the 35-year-old National Assembly leader who declared himself interim president last month during a mass demonstration against the government. At least seven European countries threw their weight behind Mr. Guaidó on Monday, raising pressure on Mr. Maduro.

The crisis, years in the making, has left many of Venezuela’s roughly 31 million people destitute and hungry, sent more than two million people into neighboring countries as refugees and created a new source of instability in Latin America. The outcome of the struggle will determine who controls not only Venezuela’s government but also its proven oil reserves, which by some estimates are the world’s largest.

Here are the basics on who is with Mr. Maduro, who has turned against him — and what to expect in the next turbulent weeks:

Mr. Maduro still has powerful backers at home and abroad.

Russia in particular has propped up Mr. Maduro’s government with billions of dollars in loans, and Cuba has provided intelligence support. While Venezuela’s poorest people may be suffering the most as the economy stagnates and institutions crumble, many remain loyal to Mr. Maduro as the heir to Hugo Chávez, the longtime socialist leader who commanded an enormous following. And one of Mr. Maduro’s firmest pillars of support, the military, remains officially on his side — although critics say cracks are showing.