"If, as a voter, you think what we need is more Republicans in Washington to cut a deal with Harry Reid and Nancy Pelosi and Chuck Schumer, then I guess Donald Trump's your guy."

Republican Sen. Ted Cruz of Texas spoke those words in Manchester, N.H., in January 2016. The events of last week prove that Cruz was at least partly right.

The senator was not alone in arguing that Trump, as president, would be quick to cut deals with the political opposition at his own allies' expense. After all, he was a businessman first, and not omitted to a specific ideological program.

To be fair to Trump, he seems mostly to have listened to and leaned on conservatives when making policy during his first seven months in office. And it took several months before he actually agreed to surrender to Democratic demands as he now has, by rolling hurricane relief and a short-term debt ceiling increase into one must-pass package. The consequences of Trump working with Democrats in this case are not too serious. Uncle Sam can keep borrowing, at least for a few more months, without any tradeoffs or limitations.

House Speaker Paul Ryan, R-Wis., was as conciliatory as possible on Thursday when he spoke at a news conference about Trump's unexpected betrayal. The president, he said, had been looking for a bipartisan moment at a time of crisis, and this seemed like a good one.

Ryan, who overcame his personal reservations to work with Trump during the 2016 election, will surely continue to work with him despite such a snub. But it has never been more important for Trump to remember who his friends are. Not all Republicans will be so good-natured as their Speaker, and the success or failure of Trump's presidency depends on their cooperation.

Democratic leaders such as House Minority Leader Nancy Pelosi, D-Calif., and Senate Minority Leader Chuck Schumer, D-N.Y., are willing to work with Trump now and then when they can belittle him by obliging him to do their bidding. It means they strategically outwit congressional Republicans and turn the tables in Washington so that they get to set the agenda once again. But no matter how much Trump works with them, Democrats are not interested in helping him achieve any of his legislative goals.

Their sole goal in 2018 is to win the midterm elections by running on the idea that Trump is the villain. This is their right as an opposition party. They are silly and vain, indulging the conceit that they are "the resistance," a popular movement fighting a quasi-Hitlerian dictatorship, when in truth they are just an out-of-touch political party that can't handle election defeat. But as silly and vain as the Democrats are, they are right in recognizing that they have nothing to gain from working with Trump.

This is why many in the House and Senate Democratic caucuses already publicly denounce him as a white supremacist, and not only find fault with his response to the violence in Charlottesville, but actually argue that he is responsible for what happened there.

Schumer, Pelosi, and the Democrats worked against Trump on his executive and judicial nominations, on his regulatory repeal efforts, and on healthcare reform. And after the Harvey bill has become law, they will work against him on tax reform and whatever comes after that. If they win the House back in 2018 they will have to fight hard to resist pressure to allow Trump to be impeached. They may not resist all that hard.

In the meantime, Trump has just snubbed the very congressional Republicans whose support he needs in order to win all the battles he will have to fight in the future.

Congress is a co-equal branch of government with the presidency, albeit a branch in which no single person holds all the power. Trump has big plans on healthcare, tax reform, and immigration reform (including both his wall and the future of those who came to the country illegally as children) to name just a few. He's going to need the help and sympathy of the congressional Republican leadership to make any of them reality.

If he really thinks he can make a better deal with Democrats and get anything done after that, Trump is in for a very rude awakening.