HARRISBURG, Pa. — Republican U.S. Sen. Pat Toomey is trying to turn his refusal thus far to endorse GOP presidential nominee Donald Trump into a strength, saying Monday there’s no evidence his Democratic challenger Katie McGinty would stand up to Democratic presidential nominee Hillary Clinton, should Clinton be elected.

In a Monday appearance at the Pennsylvania Press Club, Toomey acknowledged he is still weighing Trump’s potential to work with a Republican-controlled Congress against the candidate’s “outrageous and offensive” statements and policy positions with which Toomey disagrees.

But, he added, it is also important for a senator to be willing to stand up to his or her party’s president.

“I think the most important thing for most Pennsylvanians is not which candidate voted for which presidential nominee, (but) is which person is going to be an independent voice for Pennsylvania, who’s going to stand up to a president of either party when that president goes wrong?” Toomey said.

McGinty is broadly in line with the top priorities of President Barack Obama and Clinton, and has endorsed Clinton for president. Polling shows McGinty and Toomey in a neck-and-neck race that could decide majority control of the U.S. Senate.

Asked about it last month at the Press Club, McGinty could not name a policy disagreement with Clinton, a point that Toomey raised Monday. She went on to say that she and Clinton would bring “different approaches or different insights to tackling various issues.”

McGinty’s ties to the Clintons run deep, having worked as a top environmental policy adviser in Bill Clinton’s White House in the 1990s.

For Toomey, creating space between himself and Trump could be crucial to winning moderates and independents from which he’ll likely need strong support in a state where registered Democrats outnumber Republicans 4 to 3.

That portends another tight race for the freshman senator, who scored a 2 percentage-point victory in 2010’s Republican wave and has a lifetime rating by the American Conservative Union that makes him 13th most conservative senator.

Toomey has made clear that he finds Clinton unacceptable, and he has opposed Obama’s major policies. But Toomey’s refusal to back the billionaire developer has played poorly at times with bedrock Republicans who support Trump, and Toomey has been confronted at various campaign stops about it. At one such meet-and-greet in Carlisle in late July, Cumberland County’s GOP chairman, Greg Rothman, defended Toomey.

“I know who Senator Toomey’s going to vote for for president,” he told the gathering at the Market Cross Pub and Brewery.

McGinty’s campaign said Monday that Clinton and McGinty will “of course” disagree on certain issues, such as on how to deal with the Guantanamo Bay prison.

“On the other hand, it’s unacceptable that Pat Toomey doesn’t have the courage to stand up to Donald Trump, a racist, bigoted scam artist,” the McGinty campaign said.

For his part, Toomey in May hedged on his long-stated intent to support the eventual GOP presidential nominee and in interviews and editorials published in major newspapers laid out a long list of concerns he has with Trump.

His complaints included Trump’s lack of devotion to conservative fiscal principles, his vulgarity, and his vagueness about what he would do as president — or how.

On Monday, Toomey reiterated that he has not written off Trump, and said that Trump as president could work with a Republican-controlled Congress to repeal Obama’s signature health care law, impose more sanctions on Iran and cut taxes.

“I hope to get to the point where I can enthusiastically support Donald Trump, and I do think there’s some important things we can do,” Toomey said.