Pat Toomey is a Republican U.S. senator from Pennsylvania

Donald Trump has dominated the political discussion for the better part of the last year. While I would prefer to focus on my work in the U.S. Senate, and on my own campaign for reelection, there is an unlimited interest in all-things Trump, so I'll offer a few thoughts about the presidential race.

At the beginning of the primary process, I endorsed Marco Rubio for president. I felt then, and still do, that Rubio possessed the best combination of policy knowledge, dedication to conservative principles, and an inspiring vision to successfully lead our country in these troubled times. I regret that he did not prevail. When the Pennsylvania primary came along last month, I made clear whom I voted for, and it was not Donald Trump.

Trump was not my first, second, or third choice. I object to much in his manner and his policies. His vulgarity, particularly toward women, is appalling. His lack of appreciation for Constitutional limits on executive powers is deeply concerning. I disagree with his proposals to ban Muslims, to give government more eminent domain powers, to be neutral between Israel and its enemies, and several others. In short, I find his candidacy highly problematic.

I find Hillary Clinton unacceptably flawed. Regarding character, there are abundant reasons to doubt her honesty. As for policy, her time as secretary of state was a total disaster for U.S. foreign policy, from the Libya debacle, to the Iran nuclear deal, to relations with a Russian dictator who is set on bullying his neighbors. A Clinton presidency would undoubtedly be nothing more than an extension of the failed status quo; in fact, her candidacy is dedicated to that very objective. That would mean more economic stagnation, and more national security weakness. That is certainly not something I could support.

As a result, like many Pennsylvanians, I'm not pleased with the two choices we have.

As a Republican elected official, I am inclined to support the nominee of my party. That doesn't mean I must always agree with him. I didn't agree with Mitt Romney, John McCain, or George W. Bush on everything, but I supported them. That said, Trump is different from previous nominees. There could come a point at which the differences 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. It is up to Trump to make the case for himself in a way that reassures the millions of Republicans and non-Republicans who have grave doubts about him. Winning the nomination is a great accomplishment, but it does not mean party members check their judgment at the door.

I've never met or spoken with Donald Trump. He certainly has never asked me for advice. But I'll offer some anyway.

To Mr. Trump: You should look at your present position as an opportunity. In fact, it's an opportunity of a lifetime. There are tens of millions of Americans who are strongly dissatisfied with the direction of our country and the dysfunction in Washington, and who recognize that Hillary Clinton represents four more years of the same failed policies. We want to move in a different direction. But, to put it in terms that a businessman like yourself will understand, you have not yet closed the sale. In fact, you have sown considerable doubts about yourself. Now that the primary process is over, you have another opportunity to make your case.

Start by uniting the Republican Party that you seek to lead. Convince us that you are committed to the principles of limited government; individual freedom; a strong national defense, and a free-market economy that promotes opportunity and rejects crony capitalism.

Then you must unite our country. For too long, too many politicians have sought to divide us by race, sex, income, and geography, pitting Americans against one another in a cynical effort to advance their political interests rather than our nation. We need to recognize that our shared values and common interests are much greater than our differences.

Finally, rather than attacking those who speak a contrary word about you or your positions, consider the value of constructive advice. Many of your critics are nothing more than political opponents who want your defeat. But some of your critics actually share the deep frustration with the direction of our country and our political class that has propelled your candidacy. Sometimes your critics might have a point. If you listen more, and talk less, you might even win some of them over. You will have to in order to be successful.

@SenToomey