GOP senator facing reelection won't commit to Trump
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Sen. Pat Toomey (R-Pa.) is raising concerns that he might not be able to support Donald TrumpDonald John TrumpCNN analyst Kirsten Powers: Melania's jacket should read 'Let them eat cake' CNN's Cuomo confronts Lewandowski over 'womp womp' remark Sessions says FBI agent Peter Strzok no longer has his security clearance MORE, the latest sign of a growing split over the GOP's presumptive presidential nominee. 

"I've got this set of doubts," Toomey told WAEB, a local radio station, on Monday. "And I hope we don't get to a point where I decide I just can't support him."

Toomey added, "My message to Donald Trump is: You need to unite the Republican Party if you want to win this general election. I hope to get to the point where I can enthusiastically support Donald Trump. I'm not there right now."

Toomey is one of a handful of vulnerable GOP incumbents who are running for reelection in states previously carried by President Obama. GOP Sens. Kelly AyotteKelly Ann AyotteErnst, Fischer to square off for leadership post The Hill's Morning Report: Koch Network re-evaluating midterm strategy amid frustrations with GOP Audit finds US Defense Department wasted hundreds of millions of taxpayer dollars MORE (N.H.) Ron JohnsonRonald (Ron) Harold JohnsonSenate probes FBI's heavy-handed use of redactions to obstruct congressional investigators Hillicon Valley: DHS gets new cyber chief | White House warns lawmakers not to block ZTE deal | White nationalists find home on Google Plus | Comcast outbids Disney for Fox | Anticipation builds for report on FBI Clinton probe Graham jokes about Corker: GOP would have to be organized to be a cult MORE (Wis.), Mark KirkMark Steven KirkThis week: Trump heads to Capitol Hill Trump attending Senate GOP lunch Tuesday High stakes as Trump heads to Hill MORE (Ill.) and Rob PortmanRobert (Rob) Jones PortmanSenate moving ahead with border bill, despite Trump 13 GOP senators ask administration to pause separation of immigrant families Lawmakers, businesses await guidance on tax law MORE (Ohio) have each said they will support the party's eventual nominee.

His comments come after Trump locked down his status as the party's presumptive nominee last week when rivals Sen. Ted CruzRafael (Ted) Edward CruzSenate Gang of Four to meet next week on immigration Live coverage: High drama as hardline immigration bill fails, compromise vote delayed Trump renews call to end filibuster amid immigration furor MORE (Texas) and Ohio Gov. John Kasich dropped out of the race following Trump's victory in the Indiana primary.

Though Toomey previously suggested he would support Trump if he were the nominee, he's also tried to publicly create space between the two campaigns.

"Trump was not my first, second, or third choice. I object to much in his manner and his policies," he wrote Sunday in a Philadelphia Inquirer op-ed.

Building a wall between the two races is likely an impossible task, with strategists predicting Trump will loom over the Pennsylvania Senate contest. Katie McGinty, Toomey's Democratic opponent, has repeatedly linked the two as she seeks to unseat the GOP senator.

Trump won the state's primary earlier this year but faces an uphill battle in November. A Republican presidential candidate hasn't carried Pennsylvania since 1988.