The US president is not elected by the nationwide popular vote, but in a series of state-by-state contests.
In an election-year display of incumbent's power, Obama on Monday was declaring a national monument at the home of Latino labor leader Cesar Chavez, the United Farmworkers Union founder who died in 1993. That is designed as an open appeal to Hispanic voters in swing states, before the president moves from Los Angeles to San Francisco for more fundraising.
Romney intends his foreign policy speech as a vehicle to send tough signals on Iran and Syria and portray Obama as weak for his administration's changing explanation for the deadly attacks on the US consulate in Libya.
The Obama campaign was hitting back in advance.
"We're not going to be lectured by someone who has been an unmitigated disaster on foreign policy," Obama campaign spokeswoman Jen Psaki said.
Voters give Obama higher marks than Romney on questions of national security and crisis response, but world affairs in general are a distant priority compared with the struggling US economy, polling shows. Nevertheless, Romney will speak at Virginia Military Institute to broaden his explanation of how he would serve as commander in chief.