MOSCOW (AP) — The 15-day jail sentence imposed Monday on Alexei Navalny is nothing new for the Kremlin's most visible domestic foe, and is unlikely to be more than a brief interruption of his campaign against what he calls "the party of crooks and thieves." He's repeatedly been jailed, endured a year of house arrest and three convictions that could have brought him significant prison time.

Amid all the detentions, the 40-year-old Navalny has relentlessly pursued corruption investigations that allege the top tier of Russian officials, including Prime Minister Dmitry Medvedev, have amassed extraordinary wealth, living lives of unparalleled luxury behind their modest public images.

These claims of tainted riches have struck a chord with many Russians, who are not so moved by the more-abstract concerns of some dissidents such as freedom of speech. Protests called by Navalny took place in scores of Russian cities on Sunday, the biggest show of defiance in years.

HOW HE BEGAN

Trained as a lawyer, Navalny began his rise to prominence after he bought shares in several state-owned companies in 2008 and then pushed for access to information to which shareholders are legally entitled. His blog critiques attracted such attention that he was made a board member of state airline Aeroflot for a year. Savvy about the Internet and social media, he was able to pursue detailed open-source investigations and to disseminate the results widely to increasingly cyber-savvy Russians.

He also has a Twitter-perfect knack for pithy remarks and image-projection: His page currently features a photo of him grinning in drenching rain.

FIRST PROTEST WAVE

By 2011, when Russia held a parliamentary election rife with fraud claims, Navalny had become prominent enough to be a galvanizing figure in the call for protests. The demonstrations brought tens of thousands into the streets of Moscow and broke out in other cities as well. The size and persistence of the protests — which were held sporadically for months —appeared to take the Kremlin off guard after years of regarding opposition groups as irrelevant, if annoying, minorities.

On the eve of Vladimir Putin's inauguration for a third term as president in May 2012, police cracked down hard on protesters, arresting hundreds amid violent clashes. The crackdown appeared to sap the opposition's momentum and the Kremlin cemented its advantage by sharply increasing penalties for participating in unauthorized demonstrations — up to five years in prison for a third violation.

LEGAL PRESSURE

While the opposition staggered, Navalny was hit with complicated and dubious prosecutions for fraud and embezzlement. In one case, he and his brother Oleg were convicted of defrauding clients of a shipping business they had started. Oleg Navalny was sentenced to 3½ years in prison, but Alexei's sentence was suspended -- a move that critics said resembled Soviet-era tactics of intimidating dissidents by imprisoning their relatives.

In 2013, Alexei Navalny was convicted of embezzling timber from a state-owned company in a region where he had worked as an adviser to the governor. He was sentenced to five years in prison — but in an unprecedented move, the case's prosecutor appealed the sentence and Navalny was freed the next day. The decision appeared to reflect the Kremlin's desire to neutralize Navalny's political ambitions — the conviction would prevent him from running for office — without angering supporters enough to take to the streets.

After the European Court of Human Rights ruled he had been denied a fair trial, Navalny was again tried on the charge and again convicted in February, but given a suspended sentence.

POLITICAL FUTURE

Despite the conviction, Navalny has declared himself a candidate for next year's presidential election, in which Putin is expected to seek a fourth term. He is opening campaign offices throughout the country, expanding on experience he learned in a 2012 run for Moscow mayor — in which he came an unexpected second against Putin's favorite.

While campaigning in the Siberian city of Barnaul last week, an assailant doused Navalny's face with a bright green antiseptic liquid. Navalny used the indignity to unleash his sharp-edged humor, saying that he now looked like The Hulk.