WASHINGTON -- Walking a fine line, Sen. Pat Toomey (R., Pa.) wrote Sunday that he is "inclined" to support Donald Trump for president, but has many differences with the New York billionaire -- offering his most detailed explanation yet of how he views the controversial figure casting a shadow over Republican politics and his own re-election hopes.

"As a Republican elected official, I am inclined to support the nominee of my party," Toomey wrote Sunday in The Inquirer. "That doesn't mean I must always agree with him.

"Toomey, for example, criticized Trump's "manner and his policies," his "vulgarity, particularly toward women" and his " lack of appreciation for Constitutional limits on executive powers. But he added that Hillary Clinton is "unacceptably flawed" and would represent a continuation "of the failed status quo."

Toomey, who previously endorsed Marco Rubio for president and voted for Ted Cruz after Rubio withdrew, wrote that there "there could come a point at which the differences" with Trump "are so great as to be irreconcilable. I hope that doesn't happen, but I have never been a rubber stamp for my party's positions or its candidates."

He urged Trump to unite Republicans, and then the country, by showing he is committed to limited government, national defense and a free-market economy. (In earlier interviews, before Trump effectively sealed his win, Toomey had said he "intends" to support the GOP nominee).

The piece came as some Republicans fear Trump will lead to a down-ballot catastrophe in moderate states like Pennsylvania, potentially costing the GOP control of the Senate -- but as others argue that the unconventional developer has energized voters. Toomey is one of several senators facing difficult re-election battles in blue-leaning states.

His Democratic challenger, Katie McGinty, has seized every opportunity to link him to Trump."Pat Toomey has pledged to support the Republican presidential nominee, Donald Trump, regardless of Trump's reckless policies and speech," McGinty spokeswoman Sabrina Singh said in response.

But Toomey aimed to turn the subject to sanctuary cities -- municipalities, like Philadelphia, that cut off or limit cooperation between local police and federal authorities on immigration matters. The topic has become a flash point in the national debate over immigration.

Supporters of sanctuary cities say they prevent minor offenses from turning into life-changing deportations, and increase cooperation with police by removing immigrants' fear of being turned in to authorities. Critics, however, say such policies may let violent criminals go free. They largely point to a San Francisco killing last year, in which the accused murderer, held on a two-decade old bench warrant related to marijuana charges, had been released by local authorities despite a U.S. Immigration and Customs Enforcement request that he be detained and placed in deportation proceedings.

Toomey fired a letter to McGinty Friday urging her to join the Obama administration in calling for Philadelphia to end its sanctuary city policy -- "With 11 million people in the U.S. illegally, there are surely some violent criminals amongst them," he argued. On Monday he held a Center City press conference on the issue and, a short time later, launched a radio ad blasting McGinty on the topic.

"Pat Toomey has led the fight to stop dangerous sanctuary cities... Katie McGinty wants to keep extreme sanctuary policies in place, like Philadelphia's," the ad says, opening by saying such policies sometimes let "violent criminals loose on the streets."

Mayor Kenney has barred almost all cooperation between city police and federal immigration agents.

McGinty, in an interview in November, said local leaders should be allowed to set their law enforcement priorities, and that the real solution to the problem is comprehensive immigration reform.

"Cities are strapped and pressed for resources and I think it's important that we listen to local mayors and local police chiefs who are trying to train those resources on real public safety hazards and threats," McGinty told The Inquirer last year, before Kenney took office but while the city still functioned as a sanctuary city.

On Monday, her spokeswoman tried to draw a distinction with Philadelphia's policy, saying in an interview that McGinty believes local authorities should cooperate with the federal government when it comes to violent offenders.

"As the daughter of a Philadelphia police officer, Katie McGinty knows that public safety comes first and would work with Philadelphia and (the Department of Homeland Security) to determine the best way to keep our communities safe," Singh said in a statement.

She said Toomey "has absolutely no moral authority on this issue," since he voted against an immigration reform that passed the Senate. Advocates say the measure, which died in the House, would have resulted in a more reasonable immigration system and cut down on illegal immigration.

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