Updated 4:08 p.m. ET - STERLING, VA -- Republican presidential nominee Mitt Romney's campaign announced Monday afternoon that the candidate would add two campaign stops on Election Day in Ohio and Pennsylvania.

A campaign official said Romney would make stops in Cleveland and Pittsburgh, part of what the GOP nominee's campaign called an effort to "keep working until the polls close."

Romney campaign advisers have eyed Pennsylvania in recent weeks as a backstop against losing other battleground states, especially as Obama has managed to maintain a mostly consistent if slight advantage over Romney in Ohio. Pennsylvania lacks a robust early voting effort and the vast majority of ballots are cast on election day. Romney's campaign and outside groups supporting it have poured money into television advertising there in recent weeks.

Pittsburgh has advantage of bleeding over into the Ohio media markets, too.

David Goldman / AP

Republican presidential candidate Mitt Romney waves to supporters after finishing his speech at a campaign event at the Lynchburg Regional Airport, Monday, Nov. 5, 2012.

In Cleveland, Romney will visit his campaign's victory office, according to a Republican operative familiar with the campaign's plans.

Romney will travel to the two Midwestern battlegrounds after voting in Belmont, Massachusetts on Tuesday morning.

On Monday, Romney barnstormed across four swing states, with rallies in Florida, Virginia, Ohio and New Hampshire. The New Hampshire midnight rally in in Manchester had been billed as the campaign's finale.

Jen Psaki, the traveling campaign spokeswoman for President Barack Obama, suggested the stop was a sign of weakness.

Slideshow: Election 2012

Jim Lo Scalzo / EPA

Campaigning with Mitt Romney and Barack Obama, voting and election results.

Launch slideshow

"I will say it's no surprise that Mitt Romney is headed to Ohio, or reportedly headed to Ohio tomorrow," she told reporters in a gaggle aboard Air Force One. "Without that state it's a rocky road to victory -- an insurmountable road I would say."

Romney campaign advisers say the candidate himself decided on Monday to add the last minute stops, preferring to motivate volunteers and supporters by showing them that he was working just as hard as they are in the final hours, to sitting at home and waiting for results to come in.