MOSCOW — Dmitry Medvedev was sworn in as Russia’s third president, succeeding Vladimir Putin, with promises to fight corruption and inflation in partnership with a predecessor who may try to overshadow him.

“We must establish genuine respect for the law, to overcome legal nihilism, which seriously impedes development,” Mr. Medvedev said in a speech broadcast live on state television. He renewed his vow to fight corruption in government and society.

The new president submitted Mr. Putin’s nomination as prime minister to the State Duma hours after taking the oath of office. The lower house of parliament will consider the nomination today. Mr. Putin is also head of the United Russia party, which dominates parliament, possibly setting up a battle for leadership.

Mr. Medvedev, 42, a longtime Putin ally, assumes control of a country in its 10th straight year of economic growth. Russia, the world’s biggest energy exporter, has benefited from record oil and gas prices, with the economy growing at an average 7% a year. That growth has pushed up wages, the ruble, and inflation, making Russia less competitive. Mr. Medvedev has vowed to curb inflation, without presenting a program for doing so.

“Economically we have a big inflation problem,” the head of emerging market research at Commerzbank AG, Michael Ganske, said in a Bloomberg Television interview. “This is the problem Medvedev needs to solve to broaden his political base and gain the support of the public.”

Yevgeny Volk, a Moscow-based analyst for the Heritage Foundation, an American research group, said a power struggle between Messrs. Medvedev and Putin is likely.

“I believe Putin wants to return to power as president,” he said in an interview. “This could become a source of tension between him and Medvedev. Medvedev could very quickly acquire a taste for power.”

Mr. Medvedev said the “maturity and effectiveness of the legal system is am important condition for the development of the economy and the social sphere, support for entrepreneurialism and the battle with corruption.” He has said curbing corruption will be a priority during his presidency.

“Every Russian leader since Gorbachev and Yeltsin made the same promises at the start of their term, but unfortunately little was done to implement these promises,” Mr. Volk said. He described Mr. Medvedev as an “apparatchik” who will “protect the system of crony capitalism in today’s Russia.”

In Washington, Senator McCain said he hoped Mr. Medvedev’s ascension will start “a new era” in American-Russian relations. He urged the new president to “begin restoring and strengthening the institutions of democracy, including a free press and the rights of a vibrant Russian political opposition.”

In a statement, the Arizona senator also called on Mr. Medvedev to “ease tensions with Georgia” by reversing Russia’s recent moves to strengthen ties with the breakaway Georgian provinces of Abkhazia and South Ossetia. Mr. McCain said those moves undermine Georgian sovereignty.

Mr. McCain has previously called for Russia to be expelled from the G-8 club of industrial nations in punishment for its attempts to intimidate former Soviet republics and rollbacks of domestic freedoms. He didn’t repeat that call in his statement.