CHARLOTTESVILLE, Virginia (Reuters) - The White House says President Barack Obama is not monitoring the Republican national convention this week.

But the president told several thousand mostly college-age voters on Wednesday that they should be watching the event to help them decide how to vote in the November elections.

"In November, your voice will matter more than ever. And listen, if you doubt that, pay a little attention to what's happening in Tampa this week," Obama said.

Campaigning in Charlottesville, Virginia, the Democratic president said his focus was on Hurricane Isaac as it hit the Gulf coast, and he wanted to "make sure we are doing every single thing that we need to do" to help those affected by the storm.

Obama, in several campaign stops this week and in a brief television address, has reminded voters that he is keeping an eye on the storm -- a not-so-subtle reference to criticism that his predecessor, George W. Bush, was slow to respond to the devastation of Hurricane Katrina when it hit the same area as Isaac seven years ago.

The president began his speech on Wednesday in Virginia by saying he had just discussed Hurricane Isaac by telephone with the Federal Emergency Management Agency Administrator Craig Fugate and Homeland Security Secretary Janet Napolitano, as well as some of the mayors and governors having to deal with the storm.

It was important, Obama said, to "let people on the coast know, our thoughts are with you, our prayers are with you."

Floodwater from Hurricane Isaac jumped a levee on the outskirts of New Orleans on Wednesday, but the multi-billion-dollar barriers built to protect the city itself after the 2005 Katrina disaster held firm, officials said.

Later Wednesday, on the online chat site Reddit, Obama also expressed concern about the hurricane. He said the federal government would be coordinating with state and local officials to "make sure that we give families everything they need to recover."

The lumbering cyclone, which weakened to a tropical storm, threatened to flood oil refineries and towns in Louisiana and neighboring Mississippi with a deluge of rain, storm surges and strong winds.

(Reporting By Susan Cornwell; Editing by Fred Barbash and Cynthia Osterman)