President Donald Trump with German Chancellor Angela Merkel. Thomson Reuters Back in 2014, Sen. Bob Corker of Tennessee said then-President Barack Obama "cannot be counted on."

Corker, now the Republican chairman of the Senate Foreign Relations Committee, complained that Obama had failed to follow through on promises to groups in Libya and Syria.

But Obama's "empty promises and unreliability are at their most acute in Eastern Europe," Corker wrote. "Our tepid response to Russian aggression in Ukraine for nearly five months emboldened Putin, directly undermining US interests and making Europe, and thus the United States, less secure."

So what did Corker say after President Donald Trump's first trip abroad, a trip on which Trump alienated NATO leaders and emboldened Putin by refusing to affirm Article 5, the provision of the NATO treaty committing members to mutual defense — and a trip that led to open rebukes of Trump from the leaders of France and Germany?

Corker — a man who is generally discussed as one of the remaining serious people in the Republican Party — said Trump's trip was "executed to near perfection."

What Trump has done in Europe was supposed to be Republicans' greatest foreign-policy fear. Trump is demonstrating that America's most important treaty commitments are unreliable, at least as long as he is president, and European leaders are reacting the way you might expect to America's declaration of its own unreliability.

German Chancellor Angela Merkel is talking openly of the fact that Germany can no longer depend on the US for its defense. Seventy years of American foreign policy in Europe — keep the Americans in, the Russians out, and the Germans down — is at risk of coming apart.

And Republican politicians are reacting like coffee-drinking fire dog, demonstrating that they never had any principles about foreign policy.

CNN anchor Anderson Cooper had to apologize earlier this month for observing — accurately, if crudely — that if Trump took a dump on his desk, CNN contributor Jeffrey Lord would defend it.

We learned last week that the situation was actually worse than that: Trump could go to Europe and take a dump on the NATO alliance, and Republican politicians would say he executed the dump to perfection.