Romney is set to campaign in the southern state of Florida, while Ryan is heading to the midwestern state of Iowa.
The two campaigned Sunday in North Carolina and then in Ryan's home state of Wisconsin. Both states are considered key battlegrounds in the race for the White House.
Ryan told cheering supporters, "We can get this country back on track. We can get our people back to work. We can get our debt paid off so we can give our children a better standard of life."
President Barack Obama, speaking at a campaign fundraiser in his hometown of Chicago on Sunday, called Ryan a "decent man" and a "family man" who is "an articulate spokesman for Governor Romney's vision" - a vision the president said he "fundamentally" disagrees with.
Obama said Romney and Ryan believe getting rid of regulations on big corporations and giving tax breaks to the wealthiest Americans "will lead to jobs and prosperity for everybody else." He called this "trickle-down fairy dust" that has not worked in the past.
Romney is hoping Ryan's work in Congress to cut spending and create smaller government will help energize the Republican Party's conservative base.
They launched their four-day, multi-state campaign bus tour on Saturday, immediately after Romney announced the 42-year-old congressman as his vice presidential pick.
Romney, the presumptive Republican nominee, will face President Obama, a Democrat, in the November 6 election.
Some information for this report was provided by AP and Reuters.
