According to the survey, many Trump-supporters don't think there's anything to worry about as far as Democrats taking over Congress after the midterm elections.

A private poll commissioned by the Republican National Committee and obtained by Bloomberg has some sobering news for the GOP.

President Trump's boasts that a "red wave" could increase Republican majorities appear to have lulled GOP voters into complacency, raising the question of whether they'll turn up at the polls. While most election forecasters, as well as strategists in both parties, believe Democrats are likely to win the 23 seats necessary to take control of the House of Representatives, Republican voters aren't convinced, the survey shows. According to the RNC study, completed on Sept. 2 by the polling firm Public Opinion Strategies, most voters believe Democrats will win back the House – just not Republican voters. Fully half of self-identified Republicans don't believe Democrats are likely to win back the House. And within that group, 57 percent of people who describe themselves as strong Trump supporters don't believe Democrats have a chance (37 percent believe they do). If overconfident Republican voters stay home, Democrats could win a landslide. The report urges GOP officials to yank their voters back to reality: "We need to make real the threat that Democrats have a good shot of winning control of Congress. The president instead has delivered the opposite message. At rallies and on Twitter, Trump has claimed that – contrary to conventional wisdom and polling – Republicans might actually increase their margin in November. The internal RNC study finds that complacency among GOP voters is tied directly to their trust in the president – and their distrust of traditional polling.

This is an internal poll, never meant to be made public. For those who believe – sometimes rightly and sometimes wrongly – that polls are rigged in favor of the Democrats, the fact that the poll was not for public consumption should be a sobering revelation.

The "blue wave" is vastly overblown. Those who confidently predict Democratic gains of 50 seats or more are engaged in wishful thinking. But the Republicans' problem is that there are about 40 open seats due to retirements or lawmakers not running for re-election to Congress in order to run for other offices. Many of those open seats are in strong GOP districts, where a Republican successor is likely. But along with the number of vulnerable Republicans running in districts won by Hillary Clinton in 2016, the risk of a Democratic takeover is real.

Trump and other Republicans talking about a red wave should cool it. The party that holds the White House and Congress has only increased its majority twice in the first off year election: FDR in 1934 and George Bush in 2002. With the kind of complacency evident in that internal poll, there is a real risk that what might have been an election with modest gains by Democrats short of a majority will turn into a disaster.