HARRISBURG, Pa. (AP) — U.S. Sen. Bob Casey, fresh off winning a third term in office, is floating the idea of running for president and saying he is battle-tested in a state critical for him and his fellow Democrats in 2020.

Casey's campaign bolstered the approach Monday, releasing a memo that makes the case for electoral effectiveness in Pennsylvania, which was a stepping stone in President Donald Trump's path to the White House.

Casey said that he won his race on the issues he believes will be most prominent in a presidential campaign — health care and the middle class among them — and that he won in a state that is a must-win for Democrats running for president.

"For a Democrat, if you lose Pennsylvania, it's game over, you can't win, the math doesn't work," he said in an interview Monday. "And I want to make sure that our nominee can win this state."

Harry Truman in 1948 was the last Democratic presidential candidate to lose Pennsylvania but win the election, while Republicans can secure the White House without Pennsylvania. Trump didn't need Pennsylvania to secure the White House but became the first Republican presidential nominee to win it since 1988.

Casey, the 58-year-old son of the late two-term governor of the same name, said that his thinking is still in its early stages and that he has given himself no timetable to make a decision.

He has plenty of company.

"I think it'd be easier to look around the Senate Democratic caucus and see who's not running," said Christopher Nicholas, a Pennsylvania-based Republican campaign strategist.

Casey's father also considered a run in 1996 during the primaries, after the anti-abortion Roman Catholic governor was denied a chance to address the 1992 Democratic convention about abortion.

In the Nov. 6 election, Casey beat Republican U.S. Rep. Lou Barletta, an early supporter of Trump, who returned the favor by campaigning twice in the state for Barletta.

Casey beat Barletta by nearly 13 percentage points after heavily outraising him and boasting approval ratings that reflected no apparent weakness, backlash or scandal that is typically the undoing of an incumbent. Meanwhile, two fellow Democratic senators who are considering running for president — California's Kamala Harris and Massachusetts' Elizabeth Warren — both campaigned for Casey.

Long a favorite of labor unions, Casey is a staunch critic of Trump, criticizing the president's tax law as a giveaway to the wealthy and corporations and voting against both of Trump's Supreme Court nominees. His campaign notes that he accumulated the biggest margin of victory of the 10 Senate Democrats running for re-election this year in states carried by Trump in 2016.

Casey is ready with other points about why he fits the presidential bill.

He demonstrated that he can compete for votes in both rural and urban areas, he said. He has national security credentials after more than six years on the Senate Foreign Relations Committee and chairing a subcommittee that handled Middle Eastern affairs, he said.

Like his father, Casey has split with his party on abortion, voting for a 20-week abortion ban. Coming from an industrial state, Casey occasionally split with former President Barack Obama on environmental policy and routinely votes against trade deals, including Obama's.

Casey didn't dismiss the idea that another Democrat can win Pennsylvania, but he also warned that Trump can win Pennsylvania again.

A Pennsylvania-based Republican political strategist, Charlie Gerow, said the state, with its relatively late primary date, will be of limited value to Casey in a primary campaign. Casey, rather, might better fit the vice presidential mold, Gerow said.

Mike Mikus, a Pennsylvania-based Democratic campaign strategist, said that it is difficult to see a path to primary victory for Casey, but that a big field could help him.

"It's not crazy to see the left wing of the party splitting up votes and creating an opportunity down the middle for him," Mikus said.