FRESNO, Calif. — President Obama arrived in the heart of California’s parched farmland on Friday afternoon to offer tens of millions of dollars in federal assistance to the state, where the lack of rain and snow this winter has led to the severest drought in its modern history.

Meeting with farmers and ranchers around Fresno — where electronic signs along highways flash entreatingly to drivers, “Serious drought. Help save water” — Mr. Obama pledged $183 million from existing federal funds for drought relief programs in California. Though the announcement won cautious support in this region, Mr. Obama also pressed ahead with the more difficult task of enlisting rural America in his campaign on climate change by linking it to the drought.

The president was accompanied on his tour by the state’s top Democrats, a show of solidarity that underscored the emerging partisan battle over the management of the drought in the nation’s most populous state and the source of half of the country’s fruits and vegetables.

Seated at the center of a horseshoe table at a water district building where he met with community leaders, Mr. Obama spoke of the difficulties of dealing with the drought in the face of California’s intricate water politics, which have traditionally cleaved along regional lines and have often become mired in epic court battles.