"Paul Ryan didn’t abandon Donald Trump. Donald Trump abandoned Paul Ryan. He left him with no good option and no reason to hold on. With little time and sinking poll numbers, congressional Republicans are now fending for themselves. This was inevitable. Paul Ryan is doing his job and that’s defending the House majority."

On policy, Donald Trump is also making it more difficult for the speaker to retain his majority. This occurs both in actual policy positions and in rhetoric. For example, Donald Trump often calls for a wall along the Southern border. Many people support this policy and many others don't object, to it, even if it's not a priority for them. On policy, Trump has an acceptable position, even if I don't personally agree with it. But, insinuating that Mexicans coming into the country are criminals is offensive to a majority of the public. Both Whites and Hispanics. Sure, some are criminals. But, most are simply trying to find a better life for their families. The failure to acknowledge this is what rubs many voters the wrong way.

Trade Promotion Authority and trade generally. Debt. Russia. Syria. Just to name a few. Donald Trump's positions are at odds with where the Republican Party has been for much of its history. Take trade, for example. A majority of economists would agree that free trade has been good for the American consumer. And, a significant number also believe American exports have increased the number of jobs in the U.S. making it a net plus for the American worker. Under President George W. Bush, free trade agreements went from three to 16. I worked for President Bush for eight years and in his second administration, I served as his political director. I can't remember a single phone call over eight years from someone complaining about his views on free trade (and I received many, many phone calls on a range of topics). Yet, listen to Donald Trump and one would believe free trade (along with immigration) is the cause of many of our country's ills. This has created a conflict for many Republicans and conservative Independents. Republicans aren't singing in tune.



Then there are Donald Trump's odd views and fascination with Russia. He has praised Vladimir Putin, whose human rights violations are too numerous to state in one short op-ed. He encouraged the Russians to hack his opponent's email, and he's sloppily repeated false Russian claims. Russia also uses Donald Trump's claims to spread anti-American propaganda around the world. The Russian news service Sputnik sent a tweet claiming that Trump's claims were true — that President Obama and Secretary Clinton founded ISIS to oust President Assad of Syria.



This is an absurd statement, but Donald Trump actually said the president and Mrs. Clinton founded ISIS. No Republican candidate has ever been so irresponsible when it comes to engaging with a dangerous foreign government. This may be OK for base Republicans, but it isn't attracting new people to the party.



Politically speaking, Donald Trump isn't helping either. The hallmarks of a successful presidential campaign operation are raising over a billion dollars, building a strong ground game and advancing a robust data and analytics operation. Led by the presidential campaign, this infrastructure has historically benefited the entire ticket. Building a successful campaign is extremely difficult and it takes at least a year. It's like building a Fortune 500 company, only trying to do it overnight. There is little room for error and every day matters a great deal. It takes thousands of people, working in unison, to "pull" a party's candidates over the finish line in a close election. A strong campaign can turn out votes that wouldn't otherwise show up, sometimes as much as two or three percent. Three percent may not sound like a lot but it matters significantly to Republican congressional majorities.



But, Donald Trump hasn't built this campaign.



He certainly hasn't raised or spent the kind of personal money needed to win. He hasn't invested in field offices to the degree necessary and he's been very late to come around on data and analytics, once famously saying data were "overrated." If data were overrated, data scientists wouldn't be such a hot commodity in both business and politics.



For nearly two years, the Clinton campaign has been meticulously building the kind of operation necessary to win. She's raised all the money she needs, so much so that her Super Pac, Priorities USA, is reported to be moving on to the U.S. Senate.



So, what is Paul Ryan to do? Given Trump's inappropriate behavior, Paul Ryan doesn't have a personal reason to support him. There's been no real policy reason to support him either. And the one thing a House Speaker can usually count on — a robust campaign operation — doesn't exist.



Paul Ryan didn't abandon Donald Trump. Donald Trump abandoned Paul Ryan. He left him with no good option and no reason to hold on. With little time and sinking poll numbers, congressional Republicans are now fending for themselves. This was inevitable. Paul Ryan is doing his job and that's defending the House majority.



Commentary by Sara Taylor Fagen, a partner at DDC Advocacy and a former political director for President George W. Bush. Follow her on Twitter @sarafagen2.



For more insight from CNBC contributors, follow @CNBCopinion on Twitter.

