* Obama to raise cash while advocating deficit plan
* Republicans, Democrats seek advantage on economic themes
By Jeff Mason
WASHINGTON, April 20 (Reuters) - U.S. President Barack Obama will tout his plan to trim the deficit and try to excite younger voters on Wednesday in a campaign-style trip to California that features a stop at Facebook headquarters.
Obama embarks on a deficit-cutting road show as policy makers and financial markets recover from ratings agency Standard & Poor's threat to downgrade America's triple-A credit rating on worries Washington won't address its fiscal woes.
The president has proposed cutting $4 trillion from the U.S. budget deficit over 12 years through spending cuts and tax hikes on the wealthiest Americans -- a plan that Republicans vehemently reject.
The question of how to rein in the deficit, which is projected to hit $1.4 trillion this fiscal year, has risen to the top of the political agenda for the 2012 presidential and congressional campaigns, and Democrats and Republicans are eager to gain traction for their respective proposals.
Obama laid out his plan last week and has been testing out talking points since formally declaring himself a candidate for re-election earlier this month.
His three-day trip to California and Nevada will give him a chance to engage with voters on deficit reduction and other economic issues while raising funds for his campaign war chest.
The president's first stop on Wednesday will be at Facebook, the social networking giant, where he will hold an online question and answer session.
The event is designed to help Obama reach tech-savvy, younger voters as his campaign ramps up use of new media to raise money and generate hype about his re-election bid.
Obama, who says he will put off formal campaigning while concentrating on his White House duties, is getting a jump on his potential Republican rivals, most of whom have yet to formally declare their candidacies.
By focusing on the economy at events in two politically important states, the president hopes to engage on an issue that his future opponents are likely to exploit as a political weakness. A Washington Post poll on Tuesday showed Obama's approval ratings near record lows because of deepening economic pessimism among Americans.
Republicans have lambasted Obama for not giving more details about his deficit-cutting plan and say tax hikes would hurt the fragile U.S. economic recovery.
Focusing so much political energy on the deficit is a major shift in itself, analysts said.
"Now that is all everybody is talking about ... reducing the deficit," said Nigel Gault, an economist at Global Insight. "The terms of the debate have changed. That is progress."