US Vice President Kamala Harris has indirectly criticised former president Donald Trump, suggesting her opponent in the November 5 election is a “coward” whose politics focus on putting down rivals.

The remarks came in a campaign appearance in the critical battleground state of Pennsylvania with running mate Minnesota Governor Tim Walz, before Harris heads to the Democratic National Convention in Chicago, which kicks off on Monday (US time).

“Over the last several years, there’s been this kind of perversion that has taken place, I think, which is to suggest that the measure of the strength of a leader is based on who you beat down. When what we know is the real and true measure of the strength of a leader is based on who you lift up,” Harris told a crowd of supporters.

“Anybody who’s about beating down other people is a coward.”

She did not directly name Trump, who in a campaign appearance on Saturday in eastern Pennsylvania referred to Harris as a “radical” and a “lunatic.”

Opinion polls have shown Harris bringing fresh energy to the Democratic presidential election campaign and closing the gap with Trump both nationally and in many of the eight highly competitive states, including Pennsylvania, that will play a decisive role in picking President Joe Biden’s successor.

Harris, who is black and has Asian heritage, will be the first woman president if she wins in November.

She said she had nearly finished writing the speech she will deliver to accept the Democratic presidential nomination on Thursday.

“There will be a lot that is about what I believe is a way forward, a new way forward, and bringing everyone along in that,” she said outside a restaurant.

Trump on Saturday said he believed Harris would be easier to beat than Biden, 81, who dropped out last month under pressure from his own party after a disastrous debate against Trump.

Pennsylvania was one of three Rust Belt states, along with Wisconsin and Michigan, that helped power Republican Trump’s upset victory in the 2016 election.

Biden, who grew up in Scranton, Pennsylvania, flipped the trio back to the Democrats in 2020. Harris aims to hold on to them in November.

Sources said on Saturday Harris is likely to join Biden on stage at the convention on Monday as he passes the torch to her as the party’s nominee for president.

The Trump campaign will try to counter-program the convention with a series of swing-state events this week.

He will visit a manufacturing plant in York, Pennsylvania, on Monday, where his campaign says he will focus on the economy.

He will also visit a county sheriff’s office in Howell, Michigan, on Tuesday to talk about safety and crime.

Trump and his running mate, Senator JD Vance, will travel to Asheboro, North Carolina, on Wednesday to speak on national security.

On Friday, Trump will join Turning Point Action, a group founded by conservative activist Charlie Kirk, for a rally in Glendale, Arizona, aimed in part at highlighting efforts to boost turnout.

Trump supporters have said they hope he will refocus his campaign on policy rather than the repeated personal attacks against Harris that he has leaned heavily on in the weeks since she emerged as the Democratic candidate.

“President Trump can win this election. His policies are good for America and if you have a policy debate he wins. Donald Trump the provocateur, the showman, may not win this election,” Republican US Senator Lindsey Graham said on NBC’s Meet the Press on Sunday.

“Policy is the key to the White House.”