Vice President Kamala Harris and former President Donald Trump will take their fight for Pennsylvania to opposite ends of the state on Monday, with Harris speaking in the northwest corner of Erie and Trump in the southeastern suburbs of Philadelphia.

Harris and Trump have been making regular appearances in what is the country's largest battleground state — it will be Harris' 10th visit to Pennsylvania this campaign season, and just last week Trump made stops in both Scranton and Reading.

Pennsylvania's energy industry and natural gas fracking are likely topics as they compete for the fraction of the state's voters who have not made up their minds. Mail-in voting is well underway in the state where some 7 million people are likely to cast votes in the presidential race.

Trump beat Hillary Clinton by more than 40,000 votes in Pennsylvania on his way to winning the presidency in 2016, but native Scrantonian Joe Biden edged Trump by about 80,000 votes in the state four years ago.

Harris will be holding a rally in Erie, a Democratic majority city of about 94,000 people bordered by suburbs and rural areas with significant numbers of Republicans. Erie County is often cited as one of the state's reliable bellwether regions, where the electorate has a decidedly moderate voting record. Trump visited Erie on Sept. 29.

Trump plans a town hall Monday at the Greater Philadelphia Expo Center and Fairgrounds in suburban Oaks, hoping to drive up turnout among his supporters.

Pennsylvania's 19 electoral votes, the most of any swing state, have long made it a center of presidential electioneering. Democrats have won three straight elections for governor and both current U.S. senators are Democrats, but its legislature is closely divided and both parties have had recent success in statewide contests.