Donald Trump laid into Obamacare again on his first stop on Sunday in Iowa
Northern states are the focus, with both candidates due to appear in Michigan and Pennsylvania.
Mr Trump believes a recent rise in polls can help him win states formally seen as Democratic strongholds.
Mrs Clinton will continue to use A-list supporters, buoyed by two polls on Sunday giving her a 4-5 point lead.
Sunday’s campaign stops take Mrs Clinton to Ohio, Michigan, Pennsylvania and New Hampshire, while Mr Trump travels to Iowa, Minnesota, Michigan, Pennsylvania and Virginia.
Mrs Clinton will appear with him in Cleveland, home town of his NBA champion Cavaliers.
She also plans to appear in Manchester, Ohio, with Khizr Khan, the father of a fallen US Muslim soldier, who delivered an emotional attack on Mr Trump at the Democratic National Convention.
Her first stop was in the mainly African American congregation of Mount Airy Church of God in Christ in Philadelphia.
African American turnout could be key in the election. Black clergy have begun a “souls to the poll” campaign to urge people to get out and vote.
More than 40 million early voters have already cast their ballots. Reports suggest many more Latino voters are turning out early in battleground states including Florida, Arizona and Nevada compared to past elections.
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