Democrat wins in blue New Jersey, purple Virginia, and red Alabama prove that the Democrats will soon be in the ascendancy, the thinking goes. John Daniel Davidson at thefederalist.com captures the newfound Democratic optimism:

The media can't get enough of polls that say the Republicans are toast in 2018. Yet a look beyond the headlines paints a different picture.

[P]undits are beginning to murmur that the GOP should brace for huge losses in the 2018 midterms. ... It's going to be a blue wave. Democrats are going to capture a new American majority.

As Davidson adds, President Trump's seemingly "dismal" approval ratings and an unpopular "GOP-controlled" Congress don't help matters for the midterms. With a now razor-thin majority in the Senate, and just 24 seats required for the Democrats to take the House, Republicans should be concerned.

But there are two problems with the "blue wave theory of 2018." The first is that Democrats "can't agree on what the party stands for," and they don't "have a unified message to spread around the country." As Davidson says, the party has "no economic message," and "the left-wing base" of the party "seems content to go out and run on a promise to impeach the president on some grounds or other."

Consider Tuesday's politico.com headline on the replacement for Michigan rep. John Conyers as the ranking Democrat on the House Judiciary Committee: "The battle to lead Trump's potential impeachment." But anti-Trump resistance is hardly an agenda:

If they want to win in deep-red states next year, Democrats will have to offer a positive vision for the country. There's no sign so far they have one to offer.

Davidson adds that "the identity politics and strident culture war posture that characterizes the national party leadership simply won't play in deep-red states." Nor will the "embrace" of the Bernie Sanders single-payer "Medicare for all" plan by 16 prominent Democratic senators, including most of the 2020 presidential hopefuls.

Davidson notes that House minority leader Nancy Pelosi is not always as far out on the progressive limb as Bernie Sanders is.

The question is: who speaks for the Democratic Party in 2018, Pelosi or Sanders? Until Democrats can answer that question, predictions of a blue wave next year are premature.

The question itself says volumes about the Democrats' red-state prospects.

Davidson brings up the second problem with the blue wave theory: anti-Trump fever "won't sweep Republicans out of power" because Trump "actually has some legitimate accomplishments to point to at the end of his first year in office."

Even Rich Lowry, at nationalreview.com, recognizes Trump's accomplishments:

As the year ends, President Donald Trump is compiling a solid record of accomplishment. Much of it is unilateral, dependent on extensive executive actions rolling back President Barack Obama's regulations, impressive judicial appointments, and the successful fight against ISIS overseas. The tax bill is the significant legislative achievement that heretofore had been missing.

Lowry says "It's hard to see how a conventional Republican would have done much better" and adds:

If any Republican would have done much of what Trump has, three acts stand out – pulling out of the Paris accords, decertifying the Iran deal, and declaring Jerusalem the capital of Israel. All three demonstrated an imperviousness to polite opinion that is one of Trump's signature qualities.

Passage of the tax cut bill also refutes the Democrat talking point that Republicans can't govern. And, as investors.com points out, widely reported negative polling results on the GOP tax bill are debunked by strongly positive results when people are asked about specific features of the tax plan – "doubling the standard deduction" and "cutting the pass-through rate for small businesses," for example.

The icing on the tax cut cake is that the GOP, with the president's encouragement, included the repeal of the Obamacare individual mandate in the final tax bill, thereby pulling the lynchpin out of the Obamacare buggy.

While the Democrats have no coherent economic message, the Trump economy has grown at 3% for the last two quarters and is forecast to hit 4% in the fourth quarter. That compares with just 2% average annual growth during the last seven Obama years. Americans love the Trump economy, even if they don't yet give Trump the credit, as newsmax.com reports:

A record number of American voters say the economy is good to excellent, the highest positive rating since the category's inception in 2001, according to the latest poll released by Quinnipiac University.

Add Trump's solid record of accomplishment to the Democrats' lack of a coherent message beyond "impeach Trump," and the blue wave theory of 2018 doesn't hold much water.